Mutations in the Leucine-Rich Repeat Kinase 2 (LRRK2) gene are intimately linked to both familial and sporadic Parkinson's disease. LRRK2 is a large protein kinase able to bind and hydrolyse GTP. A wealth of in vitro studies have established that the distinct pathogenic LRRK2 mutants differentially affect those enzymatic activities, either causing an increase in kinase activity without altering GTP binding/GTP hydrolysis, or displaying no change in kinase activity but increased GTP binding/decreased GTP hydrolysis. Importantly, recent studies have shown that all pathogenic LRRK2 mutants display increased kinase activity towards select kinase substrates when analysed in intact cells. To understand those apparently discrepant results, better insight into the cellular role(s) of normal and pathogenic LRRK2 is crucial. Various studies indicate that LRRK2 regulates numerous intracellular vesicular trafficking pathways, but the mechanism(s) by which the distinct pathogenic mutants may equally interfere with such pathways has largely remained elusive. Here, we summarize the known alterations in the catalytic activities of the distinct pathogenic LRRK2 mutants and propose a testable working hypothesis by which the various mutants may affect membrane trafficking events in identical ways by culminating in increased phosphorylation of select substrate proteins known to be crucial for membrane trafficking between specific cellular compartments.

Introduction

Parkinson's disease (PD) is a common neurodegenerative disorder of largely unknown aetiology, with ageing as a major risk factor [1]. Over a decade ago, mutations in the Leucine-Rich Repeat kinase 2 (LRRK2) gene were reported to cause autosomal-dominant PD [2,3]. Subsequent reports revealed that mutations in LRRK2 comprise the most common cause for familial PD and that several LRRK2 variants either positively or negatively correlate with PD risk [4,5], highlighting the importance of LRRK2 in disease pathogenesis.

The LRRK2 protein comprises various domains implicated in protein–protein interactions and a central region consisting of a Ras-of-complex (ROC) GTPase domain and a kinase domain connected via a C-terminal of ROC (COR) domain (Figure 1). All currently identified pathogenic mutations cluster in this central region, suggesting that targeting those activities may allow for the development of disease-modifying therapies. Towards this end, highly selective, potent and brain-permeable LRRK2 kinase inhibitors have been developed [6], and our understanding of the alterations in the catalytic activities of the various pathogenic LRRK2 mutants has greatly increased over the past years. However, there remain big gaps in our understanding of the cellular role(s) of LRRK2 in neuronal as well as non-neuronal cells, even though such understanding is critical for successfully bringing LRRK2-related drugs into the clinic.

Schematic representation of the domain structure of LRRK2, including armadillo repeats (ARM), ankyrin repeats (ANK), leucine-rich repeats (LRRs), a ROC domain, a COR domain, a kinase domain and a C-terminal WD40 domain.

Figure 1.
Schematic representation of the domain structure of LRRK2, including armadillo repeats (ARM), ankyrin repeats (ANK), leucine-rich repeats (LRRs), a ROC domain, a COR domain, a kinase domain and a C-terminal WD40 domain.

Pathogenic mutations are indicated in bold. The mutation which increases kinase activity in vitro without altering GTP binding/GTP hydrolysis is circled; the mutations which do not alter kinase activity in vitro but cause increased GTP binding/decreased GTP hydrolysis are boxed. The protective R1398H variant (or synthetic R1398L mutation) is shown in italics. For further details, see text.

Figure 1.
Schematic representation of the domain structure of LRRK2, including armadillo repeats (ARM), ankyrin repeats (ANK), leucine-rich repeats (LRRs), a ROC domain, a COR domain, a kinase domain and a C-terminal WD40 domain.

Pathogenic mutations are indicated in bold. The mutation which increases kinase activity in vitro without altering GTP binding/GTP hydrolysis is circled; the mutations which do not alter kinase activity in vitro but cause increased GTP binding/decreased GTP hydrolysis are boxed. The protective R1398H variant (or synthetic R1398L mutation) is shown in italics. For further details, see text.

LRRK2 is expressed in many tissues, suggesting that it regulates events common to various distinct cell types. Indeed, pathogenic LRRK2 has been reported to have an impact upon several conserved vesicular trafficking steps related to endocytic uptake, endosome–lysosome and autophagosome–lysosome trafficking as well as retromer-mediated trafficking to and from the Golgi complex [7]. Mechanistically, this may involve direct and/or indirect regulation of several distinct Rab proteins [714]. Rab proteins comprise a family of over 60 small GTPases which function as molecular switches, alternating between a GTP-bound active form and a GDP-bound inactive form. They are reversibly localized to distinct intracellular membranes where they interact with coat components, motor proteins and SNARE proteins to control vesicle budding, microtubule (MT)-dependent vesicle motility and vesicle fusion [15]. Interestingly, a subset of Rab proteins have recently been found to serve as LRRK2 kinase substrates, with phosphorylation thought to inactivate Rab protein function and thus the specific vesicular transport steps which these Rab proteins are regulating [14]. Since LRRK2 has also been described to bind to MT and may regulate their dynamics [16], alterations in MT stability may result in (additional) downstream effects on a vast array of vesicular trafficking routes. Here, we review current knowledge and propose a testable working model by which the distinct altered catalytic activities of the pathogenic LRRK2 mutants may have an impact upon multiple MT-mediated vesicular trafficking steps through a common mechanism.

The LRRK2 kinase and GTPase activities

A set of pathogenic LRRK2 mutations have been described, including the R1441C/G/H and N1437H mutations in the ROC domain, the Y1699C mutation in the COR domain, and the G2019S and I2020T mutations in the kinase domain (Figure 1). The most prominent G2019S mutation in the kinase domain has been consistently shown to increase LRRK2 kinase activity as assessed using in vitro phosphorylation assays [14,17,18]. Thus, the G2019S mutant may act in a gain-of-function manner, with enhanced kinase activity towards defined substrates detrimental to cell survival. Indeed, the enhanced kinase activity of the G2019S mutant has been shown to correlate with neurotoxicity which can be reverted by either pharmacological or genetic kinase inhibition [1921]. However, none of the other pathogenic mutations in the ROC or COR domain seem associated with increased inherent LRRK2 kinase activity in vitro [14,17,18].

LRRK2 is also able to bind GTP and displays inherent GTPase activity. Pathogenic mutations in the ROC and COR domain (R1441C/G, Y1699C) have been found to display increased GTP binding and decreased GTPase activity [2224], with no changes observed with the G2019S mutation [23,2527]. Interestingly, a R1398H polymorphism in the ROC domain of LRRK2 associated with decreased PD risk [5] has recently been reported to display decreased GTP binding and increased GTP hydrolysis, opposite to that reported for pathogenic mutants in the ROC and COR domain [28], and similar results have been described for an artificial R1398L mutation [2527]. These data suggest that pathogenic mutations in the ROC and COR domain increase the amount of GTP-bound LRRK2, and that such a GTP-bound form of LRRK2 may be pathogenic. In support of this view, decreasing the GTP-bound state of pathogenic LRRK2 seems beneficial to cell survival in in vitro and animal models [29], indicating that specific and brain-permeable LRRK2 GTP-binding inhibitors may provide an alternative therapeutic strategy for at least some PD cases due to mutations in the ROC and the COR domain.

Altogether, a picture has emerged whereby LRRK2-mediated pathogenicity results either from mutations which increase kinase activity without altering the GTP-bound state of LRRK2, or from mutations which increase the GTP-bound state without altering kinase activity. However, a recent seminal study found that all pathogenic LRRK2 mutants analysed (R1441C/G/H, Y1699C, G2019S, I2020T) increase the phosphorylation of a set of bona fide LRRK2 kinase substrate proteins in intact cells, whilst at the same time corroborating that only the G2019S mutant increases substrate phosphorylation when measured in in vitro phosphorylation assays using purified components [14]. Whilst awaiting independent validation by other laboratories, this is a crucially important finding, as it suggests that the distinct pathogenic LRRK2 mutants may all act through a common pathogenic mechanism by increasing the phosphorylation of LRRK2 kinase substrates in intact cells, and thus that LRRK2 kinase inhibitors may be beneficial to the entire LRRK2-linked PD spectrum.

The LRRK2 MT connection

How may pathogenic LRRK2 mutants with unaltered inherent kinase activity in vitro cause increased substrate phosphorylation in a cellular context? A wide variety of scenarios are possible. For example, the distinct pathogenic LRRK2 mutants may differentially regulate other kinases and/or phosphatases which also impinge upon the Rab substrates or their respective regulatory proteins [30] (Figure 2A,B). Indeed, various kinases and phosphatases have been reported to modulate the phosphorylation status of some Rab proteins. Whilst this is most prominently observed during mitosis [31], non-mitotic alterations in Rab phosphorylation at sites distinct from or identical to those predicted and/or shown to be phosphorylated by LRRK2 have been reported as well [3234]. However, there is currently no evidence that all pathogenic LRRK2 mutants except for the G2019S mutant regulate the activities of other kinases and/or phosphatases which have an impact upon the phosphorylation status of the select Rab proteins which are LRRK2 kinase substrates.

Possible models for how all pathogenic LRRK2 mutants may cause increased Rab protein phosphorylation in intact cells.

Figure 2.
Possible models for how all pathogenic LRRK2 mutants may cause increased Rab protein phosphorylation in intact cells.

(A) The G2019S mutant causes increased Rab protein phosphorylation due to an inherent increase in kinase activity. (B) The other pathogenic LRRK2 mutants may positively regulate kinase(s) which phosphorylate the Rab protein at the equivalent residue phosphorylated by LRRK2, or negatively regulate phosphatase(s) (PPase) which dephosphorylate the phosphorylated residue in the Rab protein. (C) Regulation of such kinases and/or phosphatases by the pathogenic LRRK2 mutants may involve direct protein–protein interactions. (D) Pathogenic LRRK2 mutants, due to enhanced GTP binding, may preferentially associate with (stable) MTs, and such increased molecular proximity may cause increased phosphorylation of Rab proteins bound to transport vesicles as they move along the MT tracks. In all cases, Rab protein phosphorylation is hypothesized to interfere with vesicular trafficking steps by currently unknown molecular mechanism(s).

Figure 2.
Possible models for how all pathogenic LRRK2 mutants may cause increased Rab protein phosphorylation in intact cells.

(A) The G2019S mutant causes increased Rab protein phosphorylation due to an inherent increase in kinase activity. (B) The other pathogenic LRRK2 mutants may positively regulate kinase(s) which phosphorylate the Rab protein at the equivalent residue phosphorylated by LRRK2, or negatively regulate phosphatase(s) (PPase) which dephosphorylate the phosphorylated residue in the Rab protein. (C) Regulation of such kinases and/or phosphatases by the pathogenic LRRK2 mutants may involve direct protein–protein interactions. (D) Pathogenic LRRK2 mutants, due to enhanced GTP binding, may preferentially associate with (stable) MTs, and such increased molecular proximity may cause increased phosphorylation of Rab proteins bound to transport vesicles as they move along the MT tracks. In all cases, Rab protein phosphorylation is hypothesized to interfere with vesicular trafficking steps by currently unknown molecular mechanism(s).

Along similar lines, the distinct pathogenic LRRK2 mutants may differentially interact with Rab kinases and/or phosphatases, altering their activities and/or substrate specificities towards the Rab substrates, thereby causing changes in the overall phosphorylation status of these proteins in intact cells (Figure 2C). Indeed, select pathogenic LRRK2 mutants have been shown to display altered interactions with various protein kinases and phosphatases [3338], but a careful side-by-side analysis of all pathogenic LRRK2 mutants with respect to those interactions, as well as the identification of the precise kinases and/or phosphatase(s) responsible for further modulating the phosphorylation status of the Rab proteins which serve as LRRK2 kinase substrates is currently missing.

Another scenario depends on differences in the subcellular localization of the distinct pathogenic LRRK2 mutant proteins. If all pathogenic LRRK2 mutants except the G2019S mutant display altered intracellular localization overlapping with that of the identified LRRK2 kinase substrate(s), such increased molecular proximity may lead to enhanced substrate protein phosphorylation similar to that mediated by the kinase-activating G2019S mutation, even though not associated with an increase in in vitro kinase activity per se (Figure 2D). Such alterations in the subcellular localization of pathogenic mutant LRRK2 proteins may further be due to GTP-binding-mediated differences in protein–protein interactions. Indeed, the large number of reported LRRK2 interactors [39,40] suggests an important role for protein interactors in regulating the cellular biology of LRRK2, even though there is currently no evidence for interactions which are selectively enhanced by all pathogenic LRRK2 mutants except for G2019S.

Since MT are required for many intracellular cargo transport processes, the reported interactions of LRRK2 with MTs warrant particular attention. Endogenous LRRK2 has been consistently shown to physically interact and co-localize with MTs [4144]. Such interactions may alter MT dynamics, with expected downstream effects on many distinct MT-mediated vesicular transport events [16]. Alternatively, MT binding may increase the amount of LRRK2 in molecular proximity to various transport vesicles which carry distinct Rab proteins, thereby locally increasing their phosphorylation status. Thus, an enhanced MT association of select pathogenic LRRK2 mutants may result in increased Rab substrate protein phosphorylation in the absence of increased inherent kinase activity, with downstream effects on vesicular trafficking steps governed by those Rab proteins.

This model predicts that all pathogenic mutants with the exception of G2019S display increased MT association, and this indeed has been described for several LRRK2 mutants when compared with G2019S [45], consistent with observations from our laboratory (unpublished). The dynamics of MT are modulated by post-translational tubulin modifications which seem to be recognized by different molecular motor proteins, thereby further contributing to the establishment and maintenance of polarized vesicular trafficking. Given that many vesicular transport events occur preferentially along stable MT tracks [16,4648], the model further predicts a preferential association of pathogenic LRRK2 with a subpopulation of stable MTs, which has been reported at least for the pathogenic R1441C and Y1699C mutants [49]. In this manner, just a few strategically placed pathogenic LRRK2 molecules, with equal inherent kinase activity when compared with the wild-type molecule, may be able to phosphorylate significant amounts of Rab proteins bound to various transport vesicles which move up and down MT tracks to their respective destinations. Interestingly, R1441C/G, Y1699C, G2019S and I2020T mutants have all been shown to enhance trans-Golgi network clustering when co-expressed with Rab7L1 [11], and primary fibroblasts from R1441C, Y1699C and G2019S LRRK2 PD patients all display the same autophagic alterations [50]. These observations suggest that all pathogenic LRRK2 mutants may converge onto the same functional outputs, even though the precise links between differential Rab phosphorylation and MT binding underlying the cellular phenotypes currently remain unknown.

Corroborating the proposed working model will require careful and correlative side-by-side analysis of all pathogenic LRRK2 mutants with respect to MT interactions, kinase activity and GTP binding. A testable prediction of this model is that the subcellular localization of all pathogenic LRRK2 mutants except for G2019S should be altered when decreasing LRRK2 GTP binding either by introducing the protective R1398H variant or by pharmacologically interfering with LRRK2 GTP binding, and decreasing GTP binding should result in decreased phosphorylation of the Rab substrate proteins mediated by all pathogenic LRRK2 mutants except for the G2019S mutant. The model further predicts that any LRRK2-mediated Rab protein phosphorylation causes deficits in vesicular trafficking, and future studies are required to determine whether LRRK2-mediated phosphorylation causes alterations in the GTP-bound (active) state of the Rab proteins, or changes in their interactions with select motor proteins, either one of which would interfere with vesicle mobility [15].

Concluding remarks

Over the past decade, significant progress has been made in our understanding of how distinct pathogenic LRRK2 mutations alter the catalytic activities of this enzyme. A picture has emerged whereby either aberrant kinase activity or an increase in the amount of GTP-bound LRRK2 may confer pathogenicity, even though the underlying mechanism(s) have remained elusive. The recent identification of Rab proteins as LRRK2 interactors and/or kinase substrates, together with the well-established role(s) of LRRK2 in MT-related processes allows for the proposal of a simple and testable working model by which all pathogenic LRRK2 mutants may culminate in identical changes in Rab-related membrane trafficking events relevant to disease pathogenesis and in a manner dependent on kinase activity. Whilst much work remains to be done to understand the cell biology underlying LRRK2-related PD, studies of this type will greatly aid in translating LRRK2 kinase inhibitors into the clinic, with a positive impact upon the life of millions of people currently suffering from this debilitating neurodegenerative disease.

Abbreviations

     
  • COR

    C-terminal of Roc

  •  
  • LRRK2

    leucine-rich repeat kinase 2

  •  
  • MT

    microtubule

  •  
  • PD

    Parkinson's disease

  •  
  • ROC

    Ras-of-complex

Funding

Work in the laboratory is supported by FEDER, grants from the Spanish Ministry of Economy and Competitiveness [grant number SAF2014-58653-R], the BBVA Foundation and the Michael J. Fox Foundation (MJFF).

Competing Interests

The Authors declare that there are no competing interests associated with the manuscript.

References

References
1
Lesage
,
S.
and
Brice
,
A.
(
2009
)
Parkinson's disease: from monogenic forms to genetic susceptibility factors
.
Hum. Mol. Genet.
18
,
R48
R59
doi:
2
Paisán-Ruíz
,
C.
,
Jain
,
S.
,
Evans
,
E.W.
,
Gilks
,
W.P.
,
Simón
,
J.
,
van der Brug
,
M.
et al. 
(
2004
)
Cloning of the gene containing mutations that cause PARK8-linked Parkinson's disease
.
Neuron
44
,
595
600
doi:
3
Zimprich
,
A.
,
Biskup
,
S.
,
Leitner
,
P.
,
Lichtner
,
P.
,
Farrer
,
M.
,
Lincoln
,
S.
et al. 
(
2004
)
Mutations in LRRK2 cause autosomal-dominant parkinsonism with pleomorphic pathology
.
Neuron
44
,
601
607
doi:
4
Bardien
,
S.
,
Lesage
,
S.
,
Brice
,
A.
and
Carr
,
J.
(
2011
)
Genetic characteristics of leucine-rich repeat kinase 2 (LRRK2) associated Parkinson's disease
.
Parkinsonism Relat. Disord.
17
,
501
508
doi:
5
Chen
,
L.
,
Zhang
,
S.
,
Liu
,
Y.
,
Hong
,
H.
,
Wang
,
H.
,
Zheng
,
Y.
et al. 
(
2011
)
LRRK2 R1398H polymorphism is associated with decreased risk of Parkinson's disease in a Han Chinese population
.
Parkinsonism Relat. Disord.
17
,
291
292
doi:
6
Taymans
,
J.-M.
and
Greggio
,
E.
(
2015
)
LRRK2 kinase inhibition as a therapeutic strategy for Parkinson's disease, where do we stand?
Curr. Neuropharmacol.
14
,
214
225
doi:
7
Gómez-Suaga
,
P.
,
Fdez
,
E.
,
Fernández
,
B.
,
Martínez-Salvador
,
M.
,
Blanca Ramírez
,
M.
,
Madero-Pérez
,
J.
et al. 
(
2014
)
Novel insights into the neurobiology underlying LRRK2-linked Parkinson's disease
.
Neuropharmacology
85
,
45
56
doi:
8
Shin
,
N.
,
Jeong
,
H.
,
Kwon
,
J.
,
Heo
,
H.Y.
,
Kwon
,
J.J.
,
Yun
,
H.J.
et al. 
(
2008
)
LRRK2 regulates synaptic vesicle endocytosis
.
Exp. Cell Res.
314
,
2055
2065
doi:
9
Gomez-Suaga
,
P.
,
Rivero-Rios
,
P.
,
Fdez
,
E.
,
Blanca Ramirez
,
M.
,
Ferrer
,
I.
,
Aiastui
,
A.
et al. 
(
2014
)
LRRK2 delays degradative receptor trafficking by impeding late endosomal budding through decreasing Rab7 activity
.
Hum. Mol. Genet.
23
,
6779
6796
doi:
10
MacLeod
,
D.A.
,
Rhinn
,
H.
,
Kuwahara
,
T.
,
Zolin
,
A.
,
Di Paolo
,
G.
,
McCabe
,
B.D.
et al. 
(
2013
)
RAB7L1 interacts with LRRK2 to modify intraneuronal protein sorting and Parkinson's disease risk
.
Neuron
77
,
425
439
doi:
11
Beilina
,
A.
,
Rudenko
,
I.N.
,
Kaganovich
,
A.
,
Civiero
,
L.
,
Chau
,
H.
,
Kalia
,
S.K.
et al. 
(
2014
)
Unbiased screen for interactors of leucine-rich repeat kinase 2 supports a common pathway for sporadic and familial Parkinson disease
.
Proc. Natl Acad. Sci. U.S.A.
111
,
2626
2631
doi:
12
Dodson
,
M.W.
,
Zhang
,
T.
,
Jiang
,
C.
,
Chen
,
S.
and
Guo
,
M.
(
2012
)
Roles of the Drosophila LRRK2 homolog in Rab7-dependent lysosomal positioning
.
Hum. Mol. Genet.
21
,
1350
1363
doi:
13
Waschbüsch
,
D.
,
Michels
,
H.
,
Strassheim
,
S.
,
Ossendorf
,
E.
,
Kessler
,
D.
,
Gloeckner
,
C.J.
et al. 
(
2014
)
LRRK2 transport is regulated by its novel interacting partner Rab32
.
PLoS One
9
,
e111632
doi:
14
Steger
,
M.
,
Tonelli
,
F.
,
Ito
,
G.
,
Davies
,
P.
,
Trost
,
M.
,
Vetter
,
M.
et al. 
(
2016
)
Phosphoproteomics reveals that Parkinson's disease kinase LRRK2 regulates a subset of Rab GTPases
.
Elife
5
.
pii: e12813
doi:
15
Stenmark
,
H.
(
2009
)
Rab GTPases as coordinators of vesicle traffic
.
Nat. Rev. Mol. Cell Biol.
10
,
513
525
doi:
16
Pellegrini
,
L.
,
Wetzel
,
A.
,
Grannó
,
S.
,
Heaton
,
G
. and
Harvey
,
K
. (
2016
)
Back to the tubule: microtubule dynamics in Parkinson's disease
.
Cell. Mol. Life Sci.
PMID:
[PubMed]
17
Jaleel
,
M.
,
Nichols
,
R.J.
,
Deak
,
M.
,
Campbell
,
D.G.
,
Gillardon
,
F.
,
Knebel
,
A.
et al. 
(
2007
)
LRRK2 phosphorylates moesin at threonine-558: characterization of how Parkinson's disease mutants affect kinase activity
.
Biochem. J.
405
,
307
317
doi:
18
Greggio
,
E
. and
Cookson
,
M.R
. (
2009
)
Leucine-rich repeat kinase 2 mutations and Parkinson's disease: three questions
.
ASN Neuro
1
,
pii: e00002
doi:
19
Greggio
,
E.
,
Jain
,
S.
,
Kingsbury
,
A.
,
Bandopadhyay
,
R.
,
Lewis
,
P.
,
Kaganovich
,
A.
et al. 
(
2006
)
Kinase activity is required for the toxic effects of mutant LRRK2/dardarin
.
Neurobiol. Dis.
23
,
329
341
doi:
20
Smith
,
W.W.
,
Pei
,
Z.
,
Jiang
,
H.
,
Dawson
,
V.L.
,
Dawson
,
T.M.
and
Ross
,
C.A.
(
2006
)
Kinase activity of mutant LRRK2 mediates neuronal toxicity
.
Nat. Neurosci.
9
,
1231
1233
doi:
21
Lee
,
B.D.
,
Shin
,
J.-H.
,
VanKampen
,
J.
,
Petrucelli
,
L.
,
West
,
A.B.
,
Ko
,
H.S.
et al. 
(
2010
)
Inhibitors of leucine-rich repeat kinase-2 protect against models of Parkinson's disease
.
Nat. Med.
16
,
998
1000
doi:
22
Lewis
,
P.A.
,
Greggio
,
E.
,
Beilina
,
A.
,
Jain
,
S.
,
Baker
,
A.
and
Cookson
,
M.R.
(
2007
)
The R1441C mutation of LRRK2 disrupts GTP hydrolysis
.
Biochem. Biophys. Res. Commun.
357
,
668
671
doi:
23
West
,
A.B.
,
Moore
,
D.J.
,
Choi
,
C.
,
Andrabi
,
S.A.
,
Li
,
X.
,
Dikeman
,
D.
et al. 
(
2006
)
Parkinson's disease-associated mutations in LRRK2 link enhanced GTP-binding and kinase activities to neuronal toxicity
.
Hum. Mol. Genet.
16
,
223
232
doi:
24
Daniëls
,
V.
,
Vancraenenbroeck
,
R.
,
Law
,
B.M.H.
,
Greggio
,
E.
,
Lobbestael
,
E.
,
Gao
,
F.
et al. 
(
2011
)
Insight into the mode of action of the LRRK2 Y1699C pathogenic mutant
.
J. Neurochem.
116
,
304
315
doi:
25
Xiong
,
Y.
,
Coombes
,
C.E.
,
Kilaru
,
A.
,
Li
,
X.
,
Gitler
,
A.D.
,
Bowers
,
W.J.
et al. 
(
2010
)
GTPase activity plays a key role in the pathobiology of LRRK2
.
PLoS Genet.
6
,
e1000902
doi:
26
Stafa
,
K.
,
Trancikova
,
A.
,
Webber
,
P.J.
,
Glauser
,
L.
,
West
,
A.B.
and
Moore
,
D.J.
(
2012
)
GTPase activity and neuronal toxicity of Parkinson's disease-associated LRRK2 is regulated by ArfGAP1
.
PLoS Genet.
8
,
e1002526
doi:
27
Biosa
,
A.
,
Trancikova
,
A.
,
Civiero
,
L.
,
Glauser
,
L.
,
Bubacco
,
L.
,
Greggio
,
E.
et al. 
(
2013
)
GTPase activity regulates kinase activity and cellular phenotypes of Parkinson's disease-associated LRRK2
.
Hum. Mol. Genet.
22
,
1140
1156
doi:
28
Nixon-Abell
,
J.
,
Berwick
,
D.C.
,
Grannó
,
S.
,
Spain
,
V.A.
,
Blackstone
,
C.
and
Harvey
,
K.
(
2016
)
Protective LRRK2 R1398H variant enhances GTPase and Wnt signaling activity
.
Front. Mol. Neurosci.
9
,
18
doi:
29
Li
,
T.
,
Yang
,
D.
,
Zhong
,
S.
,
Thomas
,
J.M.
,
Xue
,
F.
,
Liu
,
J.
et al. 
(
2014
)
Novel LRRK2 GTP-binding inhibitors reduced degeneration in Parkinson's disease cell and mouse models
.
Hum. Mol. Genet.
23
,
6212
6222
doi:
30
Barr
,
F.A.
(
2013
)
Rab GTPases and membrane identity: causal or inconsequential?
J. Cell Biol.
202
,
191
199
doi:
31
Stenmark
,
H.
(
2009
)
Rab GTPases as coordinators of vesicle traffic
.
Nat. Rev. Mol. Cell Biol.
10
,
513
525
doi:
32
Levin
,
R.S.
,
Hertz
,
N.T.
,
Burlingame
,
A.L.
,
Shokat
,
K.M.
and
Mukherjee
,
S.
(
2016
)
Innate immunity kinase TAK1 phosphorylates Rab1 on a hotspot for posttranslational modifications by host and pathogen
.
Proc. Natl Acad. Sci. U.S.A.
113
,
E4776
E4783
doi:
33
Shinde
,
S.R.
and
Maddika
,
S.
(
2016
)
PTEN modulates EGFR late endocytic trafficking and degradation by dephosphorylating Rab7
.
Nat. Commun.
7
,
10689
doi:
34
Lai
,
Y.-C.
,
Kondapalli
,
C.
,
Lehneck
,
R.
,
Procter
,
J.B.
,
Dill
,
B.D.
,
Woodroof
,
H.I.
et al. 
(
2015
)
Phosphoproteomic screening identifies Rab GTPases as novel downstream targets of PINK1
.
EMBO J.
34
,
2840
2861
doi:
35
Civiero
,
L.
,
Cirnaru
,
M.D.
,
Beilina
,
A.
,
Rodella
,
U.
,
Russo
,
I.
,
Belluzzi
,
E.
et al. 
(
2015
)
Leucine-rich repeat kinase 2 interacts with p21-activated kinase 6 to control neurite complexity in mammalian brain
.
J. Neurochem.
135
,
1242
1256
doi:
36
Parisiadou
,
L.
,
Yu
,
J.
,
Sgobio
,
C.
,
Xie
,
C.
,
Liu
,
G.
,
Sun
,
L.
et al. 
(
2014
)
LRRK2 regulates synaptogenesis and dopamine receptor activation through modulation of PKA activity
.
Nat. Neurosci.
17
,
367
376
doi:
37
Lobbestael
,
E.
,
Zhao
,
J.
,
Rudenko
,
I.N.
,
Beilina
,
A.
,
Gao
,
F.
,
Wetter
,
J.
et al. 
(
2013
)
Identification of protein phosphatase 1 as a regulator of the LRRK2 phosphorylation cycle
.
Biochem. J.
456
,
119
128
doi:
38
Athanasopoulos
,
P.S.
,
Jacob
,
W.
,
Neumann
,
S.
,
Kutsch
,
M.
,
Wolters
,
D.
,
Tan
,
E.K.
et al. 
(
2016
)
Identification of protein phosphatase 2A as an interacting protein of leucine-rich repeat kinase 2
.
Biol. Chem.
397
,
541
554
doi:
39
Manzoni
,
C.
,
Denny
,
P.
,
Lovering
,
R.C.
and
Lewis
,
P.A.
(
2015
)
Computational analysis of the LRRK2 interactome
.
PeerJ
3
,
e778
doi:
40
Porras
,
P.
,
Duesbury
,
M.
,
Fabregat
,
A.
,
Ueffing
,
M.
,
Orchard
,
S.
,
Gloeckner
,
C.J.
et al. 
(
2015
)
A visual review of the interactome of LRRK2: using deep-curated molecular interaction data to represent biology
.
Proteomics
15
,
1390
1404
doi:
41
Gandhi
,
P.N.
,
Wang
,
X.
,
Zhu
,
X.
,
Chen
,
S.G.
and
Wilson-Delfosse
,
A.L.
(
2008
)
The Roc domain of leucine-rich repeat kinase 2 is sufficient for interaction with microtubules
.
J. Neurosci. Res.
86
,
1711
1720
doi:
42
Gillardon
,
F.
(
2009
)
Leucine-rich repeat kinase 2 phosphorylates brain tubulin-beta isoforms and modulates microtubule stability — a point of convergence in parkinsonian neurodegeneration?
J. Neurochem.
110
,
1514
1522
doi:
43
Caesar
,
M.
,
Zach
,
S.
,
Carlson
,
C.B.
,
Brockmann
,
K.
,
Gasser
,
T.
and
Gillardon
,
F.
(
2013
)
Leucine-rich repeat kinase 2 functionally interacts with microtubules and kinase-dependently modulates cell migration
.
Neurobiol. Dis.
54
,
280
288
doi:
44
Law
,
B.M.H.
,
Spain
,
V.A.
,
Leinster
,
V.H.L.
,
Chia
,
R.
,
Beilina
,
A.
,
Cho
,
H.J.
et al. 
(
2014
)
A direct interaction between leucine-rich repeat kinase 2 and specific β-tubulin isoforms regulates tubulin acetylation
.
J. Biol. Chem.
289
,
895
908
doi:
45
Kett
,
L.R.
,
Boassa
,
D.
,
Ho
,
C.C.-Y.
,
Rideout
,
H.J.
,
Hu
,
J.
,
Terada
,
M.
et al. 
(
2012
)
LRRK2 Parkinson disease mutations enhance its microtubule association
.
Hum. Mol. Genet.
21
,
890
899
doi:
46
Cai
,
D.
,
McEwen
,
D.P.
,
Martens
,
J.R.
,
Meyhofer
,
E.
and
Verhey
,
K.J.
(
2009
)
Single molecule imaging reveals differences in microtubule track selection between kinesin motors
.
PLoS Biol.
7
,
e1000216
doi:
47
Jacobson
,
C.
,
Schnapp
,
B.
and
Banker
,
G.A.
(
2006
)
A change in the selective translocation of the kinesin-1 motor domain marks the initial specification of the axon
.
Neuron
49
,
797
804
doi:
48
Kaul
,
N.
,
Soppina
,
V.
and
Verhey
,
K.J.
(
2014
)
Effects of α-tubulin K40 acetylation and detyrosination on kinesin-1 motility in a purified system
.
Biophys. J.
106
,
2636
2643
doi:
49
Godena
,
V.K.
,
Brookes-Hocking
,
N.
,
Moller
,
A.
,
Shaw
,
G.
,
Oswald
,
M.
,
Sancho
,
R.M.
et al. 
(
2014
)
Increasing microtubule acetylation rescues axonal transport and locomotor deficits caused by LRRK2 Roc-COR domain mutations
.
Nat. Commun.
5
,
5245
doi:
50
Manzoni
,
C.
,
Mamais
,
A.
,
Dihanich
,
S.
,
McGoldrick
,
P.
,
Devine
,
M.J.
,
Zerle
,
J.
et al. 
(
2013
)
Pathogenic Parkinson's disease mutations across the functional domains of LRRK2 alter the autophagic/lysosomal response to starvation
.
Biochem. Biophys. Res. Commun.
441
,
862
866
doi: