1
|
Alessi DR, Pfeffer SR. Leucine-Rich Repeat Kinases. Annu Rev Biochem 2024; 93:261-287. [PMID: 38621236 DOI: 10.1146/annurev-biochem-030122-051144] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/17/2024]
Abstract
Activating mutations in leucine-rich repeat kinase 2 (LRRK2) represent the most common cause of monogenic Parkinson's disease. LRRK2 is a large multidomain protein kinase that phosphorylates a specific subset of the ∼65 human Rab GTPases, which are master regulators of the secretory and endocytic pathways. After phosphorylation by LRRK2, Rabs lose the capacity to bind cognate effector proteins and guanine nucleotide exchange factors. Moreover, the phosphorylated Rabs cannot interact with their cognate prenyl-binding retrieval proteins (also known as guanine nucleotide dissociation inhibitors) and, thus, they become trapped on membrane surfaces. Instead, they gain the capacity to bind phospho-Rab-specific effector proteins, such as RILPL1, with resulting pathological consequences. Rab proteins also act upstream of LRRK2 by controlling its activation and recruitment onto membranes. LRRK2 signaling is counteracted by the phosphoprotein phosphatase PPM1H, which selectively dephosphorylates phospho-Rab proteins. We present here our current understanding of the structure, biochemical properties, and cell biology of LRRK2 and its related paralog LRRK1 and discuss how this information guides the generation of LRRK2 inhibitors for the potential benefit of patients.
Collapse
Affiliation(s)
- Dario R Alessi
- Aligning Science Across Parkinson's (ASAP) Collaborative Research Network, Chevy Chase, Maryland, USA
- Medical Research Council Protein Phosphorylation and Ubiquitylation Unit, University of Dundee, United Kingdom;
| | - Suzanne R Pfeffer
- Aligning Science Across Parkinson's (ASAP) Collaborative Research Network, Chevy Chase, Maryland, USA
- Department of Biochemistry, Stanford University School of Medicine, Stanford, California, USA
| |
Collapse
|
2
|
van Haastert PJM, Keizer-Gunnink I, Kortholt A. Analysis of cGMP Signaling in Dictyostelium. Methods Mol Biol 2024; 2814:177-194. [PMID: 38954206 DOI: 10.1007/978-1-0716-3894-1_13] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/04/2024]
Abstract
Biochemical assays are described to analyze signal transduction by the second messenger cGMP in Dictyostelium. The methods include enzyme assays to measure the activity and regulation of cGMP synthesizing guanylyl cyclases and cGMP-degrading phosphodiesterases. In addition, several methods are described to quantify cGMP levels. The target of cGMP in Dictyostelium is the large protein GbpC that has multiple domains including a Roc domain, a kinase domain, and a cGMP-stimulated Ras-GEF domain. A cGMP-binding assay is described to detect and quantify GbpC.
Collapse
Affiliation(s)
| | - Ineke Keizer-Gunnink
- Department of Cell Biochemistry, University of Groningen, Groningen, The Netherlands
| | - Arjan Kortholt
- Department of Cell Biochemistry, University of Groningen, Groningen, The Netherlands
| |
Collapse
|
3
|
Holmes G, Ferguson SR, Lewis PA, Echeverri K. LRRK2 kinase activity is necessary for development and regeneration in Nematostella vectensis. RESEARCH SQUARE 2023:rs.3.rs-3525606. [PMID: 37986927 PMCID: PMC10659525 DOI: 10.21203/rs.3.rs-3525606/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2023]
Abstract
Background The starlet sea anemone, Nematostella vectensis, is an emerging model organism with a high regenerative capacity, which was recently found to possess an orthologue to the human LRRK2 gene (nvLRRK2). The leucine rich repeat kinase 2 (LRRK2) gene, when mutated, is the most common cause of inherited Parkinson's Disease (PD). Its protein product (LRRK2) has implications in a variety of cellular processes, however, the full function of LRRK2 is not well established. Current research is focusing on understanding the function of LRRK2, including both its physiological role as well as its pathobiological underpinnings. Methods We used bioinformatics to determine the cross-species conservation of LRRK2, then applied drugs targeting the kinase activity of LRRK2 to examine its function in development, homeostasis and regeneration in Nematostella vectensis. Results An in-silico characterization and phylogenetic analysis of nvLRRK2 comparing it to human LRRK2 highlighted key conserved motifs and residues. In vivo analyses inhibiting the kinase function of this enzyme demonstrated a role of nvLRRK2 in development and regeneration of N. vectensis. These findings implicate a developmental role of LRRK2 in Nematostella, adding to the expanding knowledge of its physiological function. Conclusions Our work introduces a new model organism with which to study LRRK biology. We show a necessity for LRRK2 in development and regeneration. Given the short generation time, genetic trackability and in vivo imaging capabilities, this work introduces Nematostella vectensis as a new model in which to study genes linked to neurodegenerative diseases such as Parkinson's.
Collapse
|
4
|
Storey CL, Williams RSB, Fisher PR, Annesley SJ. Dictyostelium discoideum: A Model System for Neurological Disorders. Cells 2022; 11:cells11030463. [PMID: 35159273 PMCID: PMC8833889 DOI: 10.3390/cells11030463] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Revised: 01/23/2022] [Accepted: 01/24/2022] [Indexed: 12/14/2022] Open
Abstract
Background: The incidence of neurological disorders is increasing due to population growth and extended life expectancy. Despite advances in the understanding of these disorders, curative strategies for treatment have not yet eventuated. In part, this is due to the complexities of the disorders and a lack of identification of their specific underlying pathologies. Dictyostelium discoideum has provided a useful, simple model to aid in unraveling the complex pathological characteristics of neurological disorders including Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, neuronal ceroid lipofuscinoses and lissencephaly. In addition, D. discoideum has proven to be an innovative model for pharmaceutical research in the neurological field. Scope of review: This review describes the contributions of D. discoideum in the field of neurological research. The continued exploration of proteins implicated in neurological disorders in D. discoideum may elucidate their pathological roles and fast-track curative therapeutics.
Collapse
Affiliation(s)
- Claire Louise Storey
- Department of Microbiology, Anatomy, Physiology and Pharmacology, La Trobe University, Bundoora 3086, Australia; (C.L.S.); (P.R.F.)
| | - Robin Simon Brooke Williams
- Centre for Biomedical Sciences, School of Biological Sciences, Royal Holloway University of London, Egham TW20 0EX, UK;
| | - Paul Robert Fisher
- Department of Microbiology, Anatomy, Physiology and Pharmacology, La Trobe University, Bundoora 3086, Australia; (C.L.S.); (P.R.F.)
| | - Sarah Jane Annesley
- Department of Microbiology, Anatomy, Physiology and Pharmacology, La Trobe University, Bundoora 3086, Australia; (C.L.S.); (P.R.F.)
- Correspondence: ; Tel.: +61-394-791-412
| |
Collapse
|
5
|
Forbes G, Schilde C, Lawal H, Kin K, Du Q, Chen ZH, Rivero F, Schaap P. Interactome and evolutionary conservation of Dictyostelid small GTPases and their direct regulators. Small GTPases 2022; 13:239-254. [PMID: 34565293 PMCID: PMC8923023 DOI: 10.1080/21541248.2021.1984829] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
GTP binding proteins known as small GTPases make up one of the largest groups of regulatory proteins and control almost all functions of living cells. Their activity is under, respectively, positive and negative regulation by guanine nucleotide exchange factors (GEFs) and GTPase activating proteins (GAPs), which together with their upstream regulators and the downstream targets of the small GTPases form formidable signalling networks. While genomics has revealed the large size of the GTPase, GEF and GAP repertoires, only a small fraction of their interactions and functions have yet been experimentally explored. Dictyostelid social amoebas have been particularly useful in unravelling the roles of many proteins in the Rac-Rho and Ras-Rap families of GTPases in directional cell migration and regulation of the actin cytoskeleton. Genomes and cell-type specific and developmental transcriptomes are available for Dictyostelium species that span the 0.5 billion years of evolution of the group from their unicellular ancestors. In this work, we identified all GTPases, GEFs and GAPs from genomes representative of the four major taxon groups and investigated their phylogenetic relationships and evolutionary conservation and changes in their functional domain architecture and in their developmental and cell-type specific expression. We performed a hierarchical cluster analysis of the expression profiles of the ~2000 analysed genes to identify putative interacting sets of GTPases, GEFs and GAPs, which highlight sets known to interact experimentally and many novel combinations. This work represents a valuable resource for research into all fields of cellular regulation.
Collapse
Affiliation(s)
- Gillian Forbes
- School of Life Sciences, University of Dundee, Dundee, UK
| | | | - Hajara Lawal
- School of Life Sciences, University of Dundee, Dundee, UK
| | - Koryu Kin
- School of Life Sciences, University of Dundee, Dundee, UK,CSIC-Universitat Pompeu Fabra, Institut de Biologia Evolutiva (Csic-universitat Pompeu Fabra), Barcelona, Spain
| | - Qingyou Du
- School of Life Sciences, University of Dundee, Dundee, UK
| | - Zhi-hui Chen
- School of Life Sciences, University of Dundee, Dundee, UK
| | - Francisco Rivero
- Centre for Atherothrombosis and Metabolic Disease, Hull York Medical School, Faculty of Health Sciences, University of Hull, Hull, UK
| | - Pauline Schaap
- School of Life Sciences, University of Dundee, Dundee, UK,CONTACT Pauline Schaap ; School of Life Sciences, University of Dundee, Msi/wtb Complex, Dundee, DD15EH, UK
| |
Collapse
|
6
|
Rosenbusch KE, Oun A, Sanislav O, Lay ST, Keizer-Gunnink I, Annesley SJ, Fisher PR, Dolga AM, Kortholt A. A Conserved Role for LRRK2 and Roco Proteins in the Regulation of Mitochondrial Activity. Front Cell Dev Biol 2021; 9:734554. [PMID: 34568343 PMCID: PMC8455996 DOI: 10.3389/fcell.2021.734554] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2021] [Accepted: 08/16/2021] [Indexed: 01/02/2023] Open
Abstract
Parkinson's Disease (PD) is the second most common neurodegenerative disease world-wide. Mutations in the multidomain protein Leucine Rich Repeat Kinase 2 (LRRK2) are the most frequent cause of hereditary PD. Furthermore, recent data suggest that independent of mutations, increased kinase activity of LRRK2 plays an essential role in PD pathogenesis. Isolated mitochondria of tissue samples from PD patients carrying LRRK2 mutations display a significant impairment of mitochondrial function. However, due to the complexity of the mitochondrial signaling network, the role of LRRK2 in mitochondrial metabolism is still not well understood. Previously we have shown that D. discoideum Roco4 is a suitable model to study the activation mechanism of LRRK2 in vivo. To get more insight in the LRRK2 pathways regulating mitochondrial activity we used this Roco4 model system in combination with murine RAW macrophages. Here we show that both Dictyostelium roco4 knockout and cells expressing PD-mutants show behavioral and developmental phenotypes that are characteristic for mitochondrial impairment. Mitochondrial activity measured by Seahorse technology revealed that the basal respiration of D. discoideum roco4- cells is significantly increased compared to the WT strain, while the basal and maximal respiration values of cells overexpressing Roco4 are reduced compared to the WT strain. Consistently, LRRK2 KO RAW 264.7 cells exhibit higher maximal mitochondrial respiration activity compared to the LRRK2 parental RAW264.7 cells. Measurement on isolated mitochondria from LRRK2 KO and parental RAW 264.7 cells revealed no difference in activity compared to the parental cells. Furthermore, neither D. discoideum roco4- nor LRRK2 KO RAW 264.7 showed a difference in either the number or the morphology of mitochondria compared to their respective parental strains. This suggests that the observed effects on the mitochondrial respiratory in cells are indirect and that LRRK2/Roco proteins most likely require other cytosolic cofactors to elicit mitochondrial effects.
Collapse
Affiliation(s)
| | - Asmaa Oun
- Department of Cell Biochemistry, University of Groningen, Groningen, Netherlands.,Groningen Research Institute of Pharmacy (GRIP), Molecular Pharmacology XB10, Groningen, Netherlands.,Department of Biotechnology, Institute of Graduate Studies and Research, Alexandria University, Alexandria, Egypt
| | - Oana Sanislav
- Department of Physiology Anatomy and Microbiology, La Trobe University, Melbourne, VIC, Australia
| | - Sui T Lay
- Department of Physiology Anatomy and Microbiology, La Trobe University, Melbourne, VIC, Australia
| | - Ineke Keizer-Gunnink
- Department of Physiology Anatomy and Microbiology, La Trobe University, Melbourne, VIC, Australia
| | - Sarah J Annesley
- Department of Physiology Anatomy and Microbiology, La Trobe University, Melbourne, VIC, Australia
| | - Paul R Fisher
- Department of Physiology Anatomy and Microbiology, La Trobe University, Melbourne, VIC, Australia
| | - Amalia M Dolga
- Groningen Research Institute of Pharmacy (GRIP), Molecular Pharmacology XB10, Groningen, Netherlands
| | - Arjan Kortholt
- Department of Cell Biochemistry, University of Groningen, Groningen, Netherlands.,Department of Pharmacology, Faculty of Medicine, Suleyman Demirel University, Isparta, Turkey
| |
Collapse
|
7
|
Bhadoriya P, Jain M, Kaicker G, Saidullah B, Saran S. Deletion of Htt cause alterations in cAMP signaling and spatial patterning in Dictyostelium discoideum. J Cell Physiol 2019; 234:18858-18871. [PMID: 30916411 DOI: 10.1002/jcp.28524] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2018] [Revised: 02/07/2019] [Accepted: 02/19/2019] [Indexed: 01/08/2023]
Abstract
In the present study, we have analyzed in detail the functions of Htt during growth and development of the protist, Dictyostelium discoideum by creating mutants (both overexpressor and knockout). The mRNA was present at all stages of growth and development. Overexpression of htt did not show any major anomaly, while deletion resulted in delayed aggregation territory formation and showed asynchronous development especially after slug stage. The slugs formed by htt - cells showed aberration in anterior-posterior boundary, showing increased prestalk region. DdHtt regulates STAT transcription factors in the tip organizer region that help maintain patterning and culmination. In chimeras with the wild-type, htt - cells preferentially localized to the tip of the slug and basal disc regions of the fruiting body showing prestalk/stalk bias, while the overexpressing cells majorly populated the prespore/spore region showing spore bias. These differences could be attributed to protein kinase A (PKA)-regulated cyclic adenosine monophosphate (cAMP) signaling.
Collapse
Affiliation(s)
- Pooja Bhadoriya
- School of Life Sciences, Jawaharlal Nehru University, New Delhi, India.,School of Sciences, Indira Gandhi National Open University, New Delhi, India
| | - Mukul Jain
- School of Life Sciences, Jawaharlal Nehru University, New Delhi, India.,School of Sciences, Indira Gandhi National Open University, New Delhi, India
| | - Geeta Kaicker
- School of Sciences, Indira Gandhi National Open University, New Delhi, India
| | - Bano Saidullah
- School of Sciences, Indira Gandhi National Open University, New Delhi, India
| | - Shweta Saran
- School of Life Sciences, Jawaharlal Nehru University, New Delhi, India
| |
Collapse
|
8
|
Williams TD, Peak-Chew SY, Paschke P, Kay RR. Akt and SGK protein kinases are required for efficient feeding by macropinocytosis. J Cell Sci 2019; 132:jcs.224998. [PMID: 30617109 DOI: 10.1242/jcs.224998] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2018] [Accepted: 12/19/2018] [Indexed: 12/20/2022] Open
Abstract
Macropinocytosis is an actin-driven process of large-scale and non-specific fluid uptake used for feeding by some cancer cells and the macropinocytosis model organism Dictyostelium discoideum In Dictyostelium, macropinocytic cups are organized by 'macropinocytic patches' in the plasma membrane. These contain activated Ras, Rac and phospholipid PIP3, and direct actin polymerization to their periphery. We show that a Dictyostelium Akt (PkbA) and an SGK (PkbR1) protein kinase act downstream of PIP3 and, together, are nearly essential for fluid uptake. This pathway enables the formation of larger macropinocytic patches and macropinosomes, thereby dramatically increasing fluid uptake. Through phosphoproteomics, we identify a RhoGAP, GacG, as a PkbA and PkbR1 target, and show that it is required for efficient macropinocytosis and expansion of macropinocytic patches. The function of Akt and SGK in cell feeding through control of macropinosome size has implications for cancer cell biology.
Collapse
Affiliation(s)
| | | | - Peggy Paschke
- MRC Laboratory of Molecular Biology, Cambridge, CB2 0QH, UK
| | - Robert R Kay
- MRC Laboratory of Molecular Biology, Cambridge, CB2 0QH, UK
| |
Collapse
|
9
|
Wauters L, Versées W, Kortholt A. Roco Proteins: GTPases with a Baroque Structure and Mechanism. Int J Mol Sci 2019; 20:ijms20010147. [PMID: 30609797 PMCID: PMC6337361 DOI: 10.3390/ijms20010147] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2018] [Revised: 12/21/2018] [Accepted: 12/25/2018] [Indexed: 01/05/2023] Open
Abstract
Mutations in leucine-rich repeat kinase 2 (LRRK2) are a common cause of genetically inherited Parkinson’s Disease (PD). LRRK2 is a large, multi-domain protein belonging to the Roco protein family, a family of GTPases characterized by a central RocCOR (Ras of complex proteins/C-terminal of Roc) domain tandem. Despite the progress in characterizing the GTPase function of Roco proteins, there is still an ongoing debate concerning the working mechanism of Roco proteins in general, and LRRK2 in particular. This review consists of two parts. First, an overview is given of the wide evolutionary range of Roco proteins, leading to a variety of physiological functions. The second part focusses on the GTPase function of the RocCOR domain tandem central to the action of all Roco proteins, and progress in the understanding of its structure and biochemistry is discussed and reviewed. Finally, based on the recent work of our and other labs, a new working hypothesis for the mechanism of Roco proteins is proposed.
Collapse
Affiliation(s)
- Lina Wauters
- VIB-VUB Center for Structural Biology, Pleinlaan 2, B-1050 Brussels, Belgium.
- Department of Cell Biochemistry, University of Groningen, NL-9747 AG Groningen, The Netherlands.
- Structural Biology Brussels, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels, Belgium.
| | - Wim Versées
- VIB-VUB Center for Structural Biology, Pleinlaan 2, B-1050 Brussels, Belgium.
- Structural Biology Brussels, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels, Belgium.
| | - Arjan Kortholt
- Department of Cell Biochemistry, University of Groningen, NL-9747 AG Groningen, The Netherlands.
| |
Collapse
|
10
|
Gilsbach BK, Eckert M, Gloeckner CJ. Regulation of LRRK2: insights from structural and biochemical analysis. Biol Chem 2018; 399:637-642. [DOI: 10.1515/hsz-2018-0132] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2018] [Accepted: 04/14/2018] [Indexed: 12/11/2022]
Abstract
Abstract
Leucine-rich repeat kinase 2 (LRRK2) is a multi-domain protein and its mutations can lead to Parkinson’s disease. Recent studies on LRRK2 and homologue proteins have advanced our mechanistic understanding of LRRK2 regulation. Here, we summarize the available data on the biochemistry and structure of LRRK2 and postulate three possible layers of regulation, translocation, monomer-dimer equilibrium and intramolecular activation of domains.
Collapse
Affiliation(s)
- Bernd K. Gilsbach
- DZNE-German Center for Neurodegenerative Diseases , Otfried-Müller Str. 23 , D-72076 Tübingen , Germany
| | - Marita Eckert
- DZNE-German Center for Neurodegenerative Diseases , Otfried-Müller Str. 23 , D-72076 Tübingen , Germany
| | - Christian Johannes Gloeckner
- DZNE-German Center for Neurodegenerative Diseases , Otfried-Müller Str. 23 , D-72076 Tübingen , Germany
- University of Tübingen, Institute for Ophthalmic Research, Center for Ophthalmology , Elfriede-Aulhorn-Str. 7 , D-72076 Tübingen , Germany
| |
Collapse
|
11
|
Mathavarajah S, Flores A, Huber RJ. Dictyostelium discoideum
: A Model System for Cell and Developmental Biology. ACTA ACUST UNITED AC 2017. [DOI: 10.1002/cpet.15] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Affiliation(s)
| | - Ana Flores
- Department of Biology, Trent University Peterborough Ontario Canada
| | - Robert J. Huber
- Department of Biology, Trent University Peterborough Ontario Canada
| |
Collapse
|
12
|
The dual enzyme LRRK2 hydrolyzes GTP in both its GTPase and kinase domains in vitro. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2016; 1865:274-280. [PMID: 27939437 DOI: 10.1016/j.bbapap.2016.12.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Revised: 11/11/2016] [Accepted: 12/06/2016] [Indexed: 11/20/2022]
Abstract
The evolutionarily conserved enzyme encoded by the leucine-rich repeat kinase 2 gene, LRRK2, harbors both a Rab-like GTPase domain and a serine/threonine protein kinase domain. Pathogenic mutations in either the GTPase or kinase domain can cause neurodegeneration and Parkinson disease. No high-resolution structure of the human LRRK2 kinase domain is available but the most common mutation, G2019S in the kinase domain, is predicted to alter the ATP-binding pocket structure and interaction with divalent cations. Here we find that the manganese-bound kinase domain acquires a robust ability to utilize both GTP as well as ATP in autophosphorylation of the GTPase domain and phosphorylation of peptide substrates in vitro. The G2019S LRRK2 mutation increases the efficiency of GTP-mediated kinase activity ten-fold compared to WT LRRK2 activity. Moreover, GTP-dependent phosphorylation alters autophosphorylation-site preference in vitro. While additional studies are required to determine the physiological relevance of these observations, LRRK2 is one of the only known kinases to be able to utilize GTP as a phospho-donor at physiological levels in vitro, and thus one of the only known proteins to be able to hydrolyze GTP in two distinct domains within the same protein.
Collapse
|
13
|
Guaitoli G, Raimondi F, Gilsbach BK, Gómez-Llorente Y, Deyaert E, Renzi F, Li X, Schaffner A, Jagtap PKA, Boldt K, von Zweydorf F, Gotthardt K, Lorimer DD, Yue Z, Burgin A, Janjic N, Sattler M, Versées W, Ueffing M, Ubarretxena-Belandia I, Kortholt A, Gloeckner CJ. Structural model of the dimeric Parkinson's protein LRRK2 reveals a compact architecture involving distant interdomain contacts. Proc Natl Acad Sci U S A 2016; 113:E4357-66. [PMID: 27357661 PMCID: PMC4968714 DOI: 10.1073/pnas.1523708113] [Citation(s) in RCA: 105] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Leucine-rich repeat kinase 2 (LRRK2) is a large, multidomain protein containing two catalytic domains: a Ras of complex proteins (Roc) G-domain and a kinase domain. Mutations associated with familial and sporadic Parkinson's disease (PD) have been identified in both catalytic domains, as well as in several of its multiple putative regulatory domains. Several of these mutations have been linked to increased kinase activity. Despite the role of LRRK2 in the pathogenesis of PD, little is known about its overall architecture and how PD-linked mutations alter its function and enzymatic activities. Here, we have modeled the 3D structure of dimeric, full-length LRRK2 by combining domain-based homology models with multiple experimental constraints provided by chemical cross-linking combined with mass spectrometry, negative-stain EM, and small-angle X-ray scattering. Our model reveals dimeric LRRK2 has a compact overall architecture with a tight, multidomain organization. Close contacts between the N-terminal ankyrin and C-terminal WD40 domains, and their proximity-together with the LRR domain-to the kinase domain suggest an intramolecular mechanism for LRRK2 kinase activity regulation. Overall, our studies provide, to our knowledge, the first structural framework for understanding the role of the different domains of full-length LRRK2 in the pathogenesis of PD.
Collapse
Affiliation(s)
- Giambattista Guaitoli
- German Center for Neurodegenerative Diseases, 72076 Tübingen, Germany; Center for Ophthalmology, Institute for Ophthalmic Research, Eberhard Karls University, 72076 Tübingen, Germany
| | - Francesco Raimondi
- Department of Life Sciences, University of Modena and Reggio Emilia, 41125 Modena, Italy; Cell Networks, University of Heidelberg, 69120 Heidelberg, Germany
| | - Bernd K Gilsbach
- German Center for Neurodegenerative Diseases, 72076 Tübingen, Germany; Department of Cell Biochemistry, University of Groningen, Groningen 9747 AG, The Netherlands; Structural Biology Group, Max Planck Institute for Molecular Physiology, 44227 Dortmund, Germany
| | - Yacob Gómez-Llorente
- Department of Structural and Chemical Biology, Icahn School of Medicine at Mount Sinai, New York, NY 10029
| | - Egon Deyaert
- Structural Biology Brussels, Vrije Universiteit Brussel, 1050 Brussels, Belgium; Vlaams Instituut voor Biotechnologie, Structural Biology Research Center, Vrije Universiteit Brussel, 1050 Brussels, Belgium
| | - Fabiana Renzi
- Department of Structural and Chemical Biology, Icahn School of Medicine at Mount Sinai, New York, NY 10029
| | - Xianting Li
- Departments of Neurology and Neuroscience, Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029
| | - Adam Schaffner
- Department of Structural and Chemical Biology, Icahn School of Medicine at Mount Sinai, New York, NY 10029; Departments of Neurology and Neuroscience, Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029
| | - Pravin Kumar Ankush Jagtap
- Center for Integrated Protein Science Munich at Department of Chemistry, Technische Universität München, 85747 Garching, Germany; Institute of Structural Biology, Helmholtz Zentrum München, 85764 Munich, Germany
| | - Karsten Boldt
- Center for Ophthalmology, Institute for Ophthalmic Research, Eberhard Karls University, 72076 Tübingen, Germany
| | - Felix von Zweydorf
- German Center for Neurodegenerative Diseases, 72076 Tübingen, Germany; Center for Ophthalmology, Institute for Ophthalmic Research, Eberhard Karls University, 72076 Tübingen, Germany
| | - Katja Gotthardt
- Structural Biology Group, Max Planck Institute for Molecular Physiology, 44227 Dortmund, Germany
| | | | - Zhenyu Yue
- Departments of Neurology and Neuroscience, Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029
| | | | | | - Michael Sattler
- Center for Integrated Protein Science Munich at Department of Chemistry, Technische Universität München, 85747 Garching, Germany; Institute of Structural Biology, Helmholtz Zentrum München, 85764 Munich, Germany
| | - Wim Versées
- Structural Biology Brussels, Vrije Universiteit Brussel, 1050 Brussels, Belgium; Vlaams Instituut voor Biotechnologie, Structural Biology Research Center, Vrije Universiteit Brussel, 1050 Brussels, Belgium
| | - Marius Ueffing
- Center for Ophthalmology, Institute for Ophthalmic Research, Eberhard Karls University, 72076 Tübingen, Germany
| | - Iban Ubarretxena-Belandia
- Department of Structural and Chemical Biology, Icahn School of Medicine at Mount Sinai, New York, NY 10029;
| | - Arjan Kortholt
- Department of Cell Biochemistry, University of Groningen, Groningen 9747 AG, The Netherlands;
| | - Christian Johannes Gloeckner
- German Center for Neurodegenerative Diseases, 72076 Tübingen, Germany; Center for Ophthalmology, Institute for Ophthalmic Research, Eberhard Karls University, 72076 Tübingen, Germany;
| |
Collapse
|
14
|
Activation Mechanism of LRRK2 and Its Cellular Functions in Parkinson's Disease. PARKINSONS DISEASE 2016; 2016:7351985. [PMID: 27293958 PMCID: PMC4880697 DOI: 10.1155/2016/7351985] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/24/2015] [Accepted: 04/19/2016] [Indexed: 01/09/2023]
Abstract
Human LRRK2 (Leucine-Rich Repeat Kinase 2) has been associated with both familial and idiopathic Parkinson's disease (PD). Although several LRRK2 mediated pathways and interaction partners have been identified, the cellular functions of LRRK2 and LRRK2 mediated progression of PD are still only partially understood. LRRK2 belongs to the group of Roco proteins which are characterized by the presence of a Ras-like G-domain (Roc), a C-terminal of Roc domain (COR), a kinase, and several protein-protein interaction domains. Roco proteins exhibit a complex activation mechanism involving intramolecular signaling, dimerization, and substrate/effector binding. Importantly, PD mutations in LRRK2 have been linked to a decreased GTPase and impaired kinase activity, thus providing putative therapeutic targets. To fully explore these potential targets it will be crucial to understand the function and identify the pathways responsible for LRRK2-linked PD. Here, we review the recent progress in elucidating the complex LRRK2 activation mechanism, describe the accumulating evidence that link LRRK2-mediated PD to mitochondrial dysfunction and aberrant autophagy, and discuss possible ways for therapeutically targeting LRRK2.
Collapse
|
15
|
Rho Signaling in Dictyostelium discoideum. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2016; 322:61-181. [DOI: 10.1016/bs.ircmb.2015.10.004] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
|
16
|
West AB. Ten years and counting: moving leucine-rich repeat kinase 2 inhibitors to the clinic. Mov Disord 2014; 30:180-9. [PMID: 25448543 PMCID: PMC4318704 DOI: 10.1002/mds.26075] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2014] [Revised: 09/29/2014] [Accepted: 09/29/2014] [Indexed: 12/22/2022] Open
Abstract
The burden that Parkinson's disease (PD) exacts on the population continues to increase year after year. Though refinement of symptomatic treatments continues at a reasonable pace, no accepted therapies are available to slow or prevent disease progression. The leucine-rich repeat kinase 2 (LRRK2) gene was identified in PD genetic studies and offers new hope for novel therapeutic approaches. The evidence linking LRRK2 kinase activity to PD susceptibility is presented, as well as seminal discoveries relevant to the prosecution of LRRK2 kinase inhibition. Finally, suggestions are made for predictive preclinical modeling and successful first-in-human trials. © 2014 The Authors. Movement Disorders published by Wiley Periodicals, Inc. on behalf of International Parkinson and Movement Disorder Society.
Collapse
Affiliation(s)
- Andrew B West
- Center for Neurodegeneration and Experimental Therapeutics, Department of Neurology, University of Alabama at Birmingham, Birmingham, Alabama, USA
| |
Collapse
|
17
|
Pfannes EKB, Anielski A, Gerhardt M, Beta C. Intracellular photoactivation of caged cGMP induces myosin II and actin responses in motile cells. Integr Biol (Camb) 2014; 5:1456-63. [PMID: 24136144 DOI: 10.1039/c3ib40109j] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Cyclic GMP (cGMP) is a ubiquitous second messenger in eukaryotic cells. It is assumed to regulate the association of myosin II with the cytoskeleton of motile cells. When cells of the social amoeba Dictyostelium discoideum are exposed to chemoattractants or to increased osmotic stress, intracellular cGMP levels rise, preceding the accumulation of myosin II in the cell cortex. To directly investigate the impact of intracellular cGMP on cytoskeletal dynamics in a living cell, we released cGMP inside the cell by laser-induced photo-cleavage of a caged precursor. With this approach, we could directly show in a live cell experiment that an increase in intracellular cGMP indeed induces myosin II to accumulate in the cortex. Unexpectedly, we observed for the first time that also the amount of filamentous actin in the cell cortex increases upon a rise in the cGMP concentration, independently of cAMP receptor activation and signaling. We discuss our results in the light of recent work on the cGMP signaling pathway and suggest possible links between cGMP signaling and the actin system.
Collapse
Affiliation(s)
- Eva K B Pfannes
- Biological Physics, Institute of Physics and Astronomy, University of Potsdam, Karl-Liebknecht-Str. 24/25, 14476 Potsdam, Germany.
| | | | | | | |
Collapse
|
18
|
Genetic, structural, and molecular insights into the function of ras of complex proteins domains. ACTA ACUST UNITED AC 2014; 21:809-18. [PMID: 24981771 PMCID: PMC4104024 DOI: 10.1016/j.chembiol.2014.05.010] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2014] [Revised: 05/13/2014] [Accepted: 05/28/2014] [Indexed: 11/22/2022]
Abstract
Ras of complex proteins (ROC) domains were identified in 2003 as GTP binding modules in large multidomain proteins from Dictyostelium discoideum. Research into the function of these domains exploded with their identification in a number of proteins linked to human disease, including leucine-rich repeat kinase 2 (LRRK2) and death-associated protein kinase 1 (DAPK1) in Parkinson’s disease and cancer, respectively. This surge in research has resulted in a growing body of data revealing the role that ROC domains play in regulating protein function and signaling pathways. In this review, recent advances in the structural information available for proteins containing ROC domains, along with insights into enzymatic function and the integration of ROC domains as molecular switches in a cellular and organismal context, are explored.
Collapse
|
19
|
Gilsbach BK, Kortholt A. Structural biology of the LRRK2 GTPase and kinase domains: implications for regulation. Front Mol Neurosci 2014; 7:32. [PMID: 24847205 PMCID: PMC4017136 DOI: 10.3389/fnmol.2014.00032] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2014] [Accepted: 04/07/2014] [Indexed: 12/20/2022] Open
Abstract
Human leucine rich repeat kinase 2 (LRRK2) belongs to the Roco family of proteins, which are characterized by the presence of a Ras-like G-domain (Roc), a C-terminal of Roc domain (COR), and a kinase domain. Mutations in LRRK2 have been found to be thus far the most frequent cause of late-onset Parkinson’s disease (PD). Several of the pathogenic mutations in LRRK2 result in decreased GTPase activity and enhanced kinase activity, suggesting a possible PD-related gain of abnormal function. Important progress in the structural understanding of LRRK2 has come from our work with related Roco proteins from lower organisms. Atomic structures of Roco proteins from prokaryotes revealed that Roco proteins belong to the GAD class of molecular switches (G proteins activated by nucleotide dependent dimerization). As in LRRK2, PD-analogous mutations in Roco proteins from bacteria decrease the GTPase reaction. Studies with Roco proteins from the model organism Dictyostelium discoideum revealed that PD mutants have different effects and most importantly they explained the G2019S-related increased LRRK2 kinase activity. Furthermore, the structure of Dictyostelium Roco4 kinase in complex with the LRRK2 inhibitor H1152 showed that Roco4 and other Roco family proteins can be important for the optimization of the current, and identification of new, LRRK2 kinase inhibitors. In this review we highlight the recent progress in structural and biochemical characterization of Roco proteins and discuss its implication for the understanding of the complex regulatory mechanism of LRRK2.
Collapse
Affiliation(s)
- Bernd K Gilsbach
- Department of Cell Biochemistry, University of Groningen Groningen, Netherlands
| | - Arjan Kortholt
- Department of Cell Biochemistry, University of Groningen Groningen, Netherlands
| |
Collapse
|
20
|
Sobczyk GJ, Wang J, Weijer CJ. SILAC-based proteomic quantification of chemoattractant-induced cytoskeleton dynamics on a second to minute timescale. Nat Commun 2014; 5:3319. [PMID: 24569529 PMCID: PMC3971484 DOI: 10.1038/ncomms4319] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2013] [Accepted: 01/25/2014] [Indexed: 01/14/2023] Open
Abstract
Cytoskeletal dynamics during cell behaviours ranging from endocytosis and exocytosis to cell division and movement is controlled by a complex network of signalling pathways, the full details of which are as yet unresolved. Here we show that SILAC-based proteomic methods can be used to characterize the rapid chemoattractant-induced dynamic changes in the actin–myosin cytoskeleton and regulatory elements on a proteome-wide scale with a second to minute timescale resolution. This approach provides novel insights in the ensemble kinetics of key cytoskeletal constituents and association of known and novel identified binding proteins. We validate the proteomic data by detailed microscopy-based analysis of in vivo translocation dynamics for key signalling factors. This rapid large-scale proteomic approach may be applied to other situations where highly dynamic changes in complex cellular compartments are expected to play a key role. Actin-dependent motility is driven by the rapid changes in the recruitment of many different structural and regulatory proteins at the cell’s cortex. Sobczyk et al. characterize these changes in the cytoskeletal proteome on a second to minute timescale during chemotactic response in Dictyostelium using SILAC-based proteomics.
Collapse
Affiliation(s)
- Grzegorz J Sobczyk
- Division of Cell and Developmental Biology, College of Life Sciences, University of Dundee, Dundee DD1 5EH, UK
| | - Jun Wang
- 1] Division of Cell and Developmental Biology, College of Life Sciences, University of Dundee, Dundee DD1 5EH, UK [2]
| | - Cornelis J Weijer
- Division of Cell and Developmental Biology, College of Life Sciences, University of Dundee, Dundee DD1 5EH, UK
| |
Collapse
|
21
|
Simple system--substantial share: the use of Dictyostelium in cell biology and molecular medicine. Eur J Cell Biol 2012. [PMID: 23200106 DOI: 10.1016/j.ejcb.2012.10.003] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Dictyostelium discoideum offers unique advantages for studying fundamental cellular processes, host-pathogen interactions as well as the molecular causes of human diseases. The organism can be easily grown in large amounts and is amenable to diverse biochemical, cell biological and genetic approaches. Throughout their life cycle Dictyostelium cells are motile, and thus are perfectly suited to study random and directed cell motility with the underlying changes in signal transduction and the actin cytoskeleton. Dictyostelium is also increasingly used for the investigation of human disease genes and the crosstalk between host and pathogen. As a professional phagocyte it can be infected with several human bacterial pathogens and used to study the infection process. The availability of a large number of knock-out mutants renders Dictyostelium particularly useful for the elucidation and investigation of host cell factors. A powerful armory of molecular genetic techniques that have been continuously expanded over the years and a well curated genome sequence, which is accessible via the online database dictyBase, considerably strengthened Dictyostelium's experimental attractiveness and its value as model organism.
Collapse
|
22
|
Roco kinase structures give insights into the mechanism of Parkinson disease-related leucine-rich-repeat kinase 2 mutations. Proc Natl Acad Sci U S A 2012; 109:10322-7. [PMID: 22689969 DOI: 10.1073/pnas.1203223109] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Mutations in human leucine-rich-repeat kinase 2 (LRRK2) have been found to be the most frequent cause of late-onset Parkinson disease. Here we show that Dictyostelium discoideum Roco4 is a suitable model to study the structural and biochemical characteristics of the LRRK2 kinase and can be used for optimization of current and identification of new LRRK2 inhibitors. We have solved the structure of Roco4 kinase wild-type, Parkinson disease-related mutants G1179S and L1180T (G2019S and I2020T in LRRK2) and the structure of Roco4 kinase in complex with the LRRK2 inhibitor H1152. Taken together, our data give important insight in the LRRK2 activation mechanism and, most importantly, explain the G2019S-related increase in LRRK2 kinase activity.
Collapse
|
23
|
|
24
|
Kortholt A, van Egmond WN, Plak K, Bosgraaf L, Keizer-Gunnink I, van Haastert PJM. Multiple regulatory mechanisms for the Dictyostelium Roco protein GbpC. J Biol Chem 2011; 287:2749-58. [PMID: 22119747 DOI: 10.1074/jbc.m111.315739] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
GbpC is a multidomain Roco protein in Dictyostelium, involved in transduction of intracellular cGMP that is produced by chemotactic signals. We have shown previously that cGMP binding to GbpC induces an intramolecular signaling cascade by activating subsequently the GEF, Ras, and kinase domains. In this study, we report on the cellular localization of GbpC. In resting cells, the protein is present in the cytoplasm, but GbpC rapidly translocates to the cell boundary upon stimulation with the chemoattractant cAMP. Also, during the formation of cell-cell streams and osmotic shock, the protein localizes toward the plasma membrane and actin cytoskeleton. The translocation upon cAMP stimulation occurs downstream of heterotrimeric G proteins but is independent of guanylyl cyclases and the previously identified cGMP-induced intramolecular signaling cascade in GbpC. Mutations in the GRAM domain of GbpC lead to disturbed membrane association and inactivation of GbpC function during chemotaxis in vivo. Furthermore, we show that the GRAM domain itself associates with cellular membranes and binds various phospholipids in vitro. Together, the results show that GbpC receives multiple input signals that are both required for functional activity in vivo. cAMP-stimulation induces a cGMP-dependent signaling cascade, leading to activation of kinase activity, and, independently, cAMP induces a GRAM-dependent translocation of GbpC toward the plasma membrane and cell cortex, where it may locally phosphorylate effector proteins, which are needed for proper biological activity.
Collapse
Affiliation(s)
- Arjan Kortholt
- Department of Cell Biochemistry, University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands
| | | | | | | | | | | |
Collapse
|
25
|
Abstract
Cells recognize external chemical gradients and translate these environmental cues into amplified intracellular signaling that results in elongated cell shape, actin polymerization toward the leading edge, and movement along the gradient. Mechanisms underlying chemotaxis are conserved evolutionarily from Dictyostelium amoeba to mammalian neutrophils. Recent studies have uncovered several parallel intracellular signaling pathways that crosstalk in chemotaxing cells. Here, we review these signaling mechanisms in Dictyostelium discoideum.
Collapse
Affiliation(s)
- Yu Wang
- Department of Cell Biology, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | | | | |
Collapse
|
26
|
Kicka S, Shen Z, Annesley SJ, Fisher PR, Lee S, Briggs S, Firtel RA. The LRRK2-related Roco kinase Roco2 is regulated by Rab1A and controls the actin cytoskeleton. Mol Biol Cell 2011; 22:2198-211. [PMID: 21551065 PMCID: PMC3128523 DOI: 10.1091/mbc.e10-12-0937] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
We identify a new pathway that is required for proper pseudopod formation. We show that Roco2, a leucine-rich repeat kinase 2 (LRRK2)-related Roco kinase, is activated in response to chemoattractant stimulation and helps mediate cell polarization and chemotaxis by regulating cortical F-actin polymerization and pseudopod extension in a pathway that requires Rab1A. We found that Roco2 binds the small GTPase Rab1A as well as the F-actin cross-linking protein filamin (actin-binding protein 120, abp120) in vivo. We show that active Rab1A (Rab1A-GTP) is required for and regulates Roco2 kinase activity in vivo and that filamin lies downstream from Roco2 and controls pseudopod extension during chemotaxis and random cell motility. Therefore our study uncovered a new signaling pathway that involves Rab1A and controls the actin cytoskeleton and pseudopod extension, and thereby, cell polarity and motility. These findings also may have implications in the regulation of other Roco kinases, including possibly LRRK2, in metazoans.
Collapse
Affiliation(s)
- Sebastian Kicka
- Section of Cell and Developmental Biology, Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093-0380, USA
| | | | | | | | | | | | | |
Collapse
|
27
|
The ROCO kinase QkgA is necessary for proliferation inhibition by autocrine signals in Dictyostelium discoideum. EUKARYOTIC CELL 2010; 9:1557-65. [PMID: 20709790 DOI: 10.1128/ec.00121-10] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
AprA and CfaD are secreted proteins that function as autocrine signals to inhibit cell proliferation in Dictyostelium discoideum. Cells lacking AprA or CfaD proliferate rapidly, and adding AprA or CfaD to cells slows proliferation. Cells lacking the ROCO kinase QkgA proliferate rapidly, with a doubling time 83% of that of the wild type, and overexpression of a QkgA-green fluorescent protein (GFP) fusion protein slows cell proliferation. We found that qkgA(-) cells accumulate normal levels of extracellular AprA and CfaD. Exogenous AprA or CfaD does not slow the proliferation of cells lacking qkgA, and expression of QkgA-GFP in qkgA(-) cells rescues this insensitivity. Like cells lacking AprA or CfaD, cells lacking QkgA tend to be multinucleate, accumulate nuclei rapidly, and show a mass and protein accumulation per nucleus like those of the wild type, suggesting that QkgA negatively regulates proliferation but not growth. Despite their rapid proliferation, cells lacking AprA, CfaD, or QkgA expand as a colony on bacteria less rapidly than the wild type. Unlike AprA and CfaD, QkgA does not affect spore viability following multicellular development. Together, these results indicate that QkgA is necessary for proliferation inhibition by AprA and CfaD, that QkgA mediates some but not all of the effects of AprA and CfaD, and that QkgA may function downstream of these proteins in a signal transduction pathway regulating proliferation.
Collapse
|