1
|
Kushwaha S, Mallik B, Bisht A, Mushtaq Z, Pippadpally S, Chandra N, Das S, Ratnaparkhi G, Kumar V. dAsap regulates cellular protrusions via an Arf6-dependent actin regulatory pathway in S2R+ cells. FEBS Lett 2024; 598:1491-1505. [PMID: 38862211 DOI: 10.1002/1873-3468.14954] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2024] [Revised: 05/05/2024] [Accepted: 05/10/2024] [Indexed: 06/13/2024]
Abstract
Membrane protrusions are fundamental to cellular functions like migration, adhesion, and communication and depend upon dynamic reorganization of the cytoskeleton. GAP-dependent GTP hydrolysis of Arf proteins regulates actin-dependent membrane remodeling. Here, we show that dAsap regulates membrane protrusions in S2R+ cells by a mechanism that critically relies on its ArfGAP domain and relocalization of actin regulators, SCAR, and Ena. While our data reinforce the preference of dAsap for Arf1 GTP hydrolysis in vitro, we demonstrate that induction of membrane protrusions in S2R+ cells depends on Arf6 inactivation. This study furthers our understanding of how dAsap-dependent GTP hydrolysis maintains a balance between active and inactive states of Arf6 to regulate cell shape.
Collapse
Affiliation(s)
- Shikha Kushwaha
- Department of Biological Sciences, Indian Institute of Science Education and Research (IISER) Bhopal, India
| | - Bhagaban Mallik
- Department of Biological Sciences, Indian Institute of Science Education and Research (IISER) Bhopal, India
| | - Anjali Bisht
- Department of Biological Sciences, Indian Institute of Science Education and Research (IISER) Bhopal, India
| | - Zeeshan Mushtaq
- Department of Biological Sciences, Indian Institute of Science Education and Research (IISER) Bhopal, India
| | - Srikanth Pippadpally
- Department of Biological Sciences, Indian Institute of Science Education and Research (IISER) Bhopal, India
| | - Nitika Chandra
- Department of Biological Sciences, Indian Institute of Science Education and Research (IISER) Bhopal, India
| | - Subhradip Das
- Department of Biological Sciences, Indian Institute of Science Education and Research (IISER) Pune, India
| | - Girish Ratnaparkhi
- Department of Biological Sciences, Indian Institute of Science Education and Research (IISER) Pune, India
| | - Vimlesh Kumar
- Department of Biological Sciences, Indian Institute of Science Education and Research (IISER) Bhopal, India
| |
Collapse
|
2
|
O'Donoghue L, Smolenski A. Roles of G proteins and their GTPase-activating proteins in platelets. Biosci Rep 2024; 44:BSR20231420. [PMID: 38808367 PMCID: PMC11139668 DOI: 10.1042/bsr20231420] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2023] [Revised: 04/30/2024] [Accepted: 05/02/2024] [Indexed: 05/30/2024] Open
Abstract
Platelets are small anucleate blood cells supporting vascular function. They circulate in a quiescent state monitoring the vasculature for injuries. Platelets adhere to injury sites and can be rapidly activated to secrete granules and to form platelet/platelet aggregates. These responses are controlled by signalling networks that include G proteins and their regulatory guanine nucleotide exchange factors (GEFs) and GTPase-activating proteins (GAPs). Recent proteomics studies have revealed the complete spectrum of G proteins, GEFs, and GAPs present in platelets. Some of these proteins are specific for platelets and very few have been characterised in detail. GEFs and GAPs play a major role in setting local levels of active GTP-bound G proteins in response to activating and inhibitory signals encountered by platelets. Thus, GEFs and GAPs are highly regulated themselves and appear to integrate G protein regulation with other cellular processes. This review focuses on GAPs of small G proteins of the Arf, Rab, Ras, and Rho families, as well as of heterotrimeric G proteins found in platelets.
Collapse
Affiliation(s)
- Lorna O'Donoghue
- UCD School of Medicine, University College Dublin, UCD Conway Institute, Belfield, Dublin 4, Ireland
- Irish Centre for Vascular Biology, Royal College of Surgeons in Ireland, 123 St. Stephen’s Green 123, Dublin 2, Ireland
| | - Albert Smolenski
- UCD School of Medicine, University College Dublin, UCD Conway Institute, Belfield, Dublin 4, Ireland
- Irish Centre for Vascular Biology, Royal College of Surgeons in Ireland, 123 St. Stephen’s Green 123, Dublin 2, Ireland
| |
Collapse
|
3
|
Zhang Y, Bai H, Zhang W, Gao J, Gao C, Deng T, Liu X, Sun X, Liu Y, Wang N, Wu Y. miR-212/132 attenuates OVA-induced airway inflammation by inhibiting mast cells activation through MRGPRX2 and ASAP1. Exp Cell Res 2023; 433:113828. [PMID: 37875175 DOI: 10.1016/j.yexcr.2023.113828] [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] [Received: 01/22/2023] [Revised: 09/25/2023] [Accepted: 10/19/2023] [Indexed: 10/26/2023]
Abstract
Allergic asthma is a chronic inflammatory disease of airways involving complex mechanisms, including MAS-related GPR family member X2 (MRGPRX2) and its orthologue MRGPRB2 on mast cells (MCs). Although miRNAs have been previously shown to related to allergic asthma, the role of miR-212/132 in this process has not been studied. In this study, the predicted pairing of miRNAs and MRGPRX2 (MRGPRB2) mRNAs was carried out by online databases and the function was verify using in vivo and in vitro experiments. Database prediction showed that miR-212/132 interact with MRGPRX2 and MRGPRB2. miR-212/132 mimics alleviated MRGPRB2 mRNA expression as well as pathology changes in lungs and AHR of mice with airway inflammation in vivo. The expression level of MRGPRB2 in the mice lungs after inhaled OVA was also decreased by miR-212/132 mimics. Meanwhile, miR-212/132 inhibited MCs degranulation and cytokines release triggered by C48/80 in vitro. Further, ASAP1 (ARF GTPase-Activating Protein 1) was selected from the junction related pathways using RNAseq and KEGG enrichment. ASAP1 mRNA level was upregulated in airway inflammation and MCs activation and decreased by miR-212/132 mimics. miR-212/132 attenuated OVA-induced airway inflammation by inhibiting MCs activation through MRGPRX2 and ASAP1.
Collapse
Affiliation(s)
- Yongjing Zhang
- The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, China; School of Pharmacy, Xi'an Jiaotong University, Xi'an, China
| | - Haoyun Bai
- School of Pharmacy, Xi'an Jiaotong University, Xi'an, China
| | - Wen Zhang
- School of Pharmacy, Xi'an Jiaotong University, Xi'an, China
| | - Jie Gao
- School of Pharmacy, Xi'an Jiaotong University, Xi'an, China
| | - Chang Gao
- School of Pharmacy, Xi'an Jiaotong University, Xi'an, China
| | - Tingting Deng
- School of Pharmacy, Xi'an Jiaotong University, Xi'an, China
| | - Xinyu Liu
- Department of Respiratory and Critical Care Medicine, The Second Affiliated Hospital of Medical College, Xi'an Jiaotong University, 157 West 5th Road, Xi'an, Shaanxi, China
| | - Xiuzhen Sun
- Department of Respiratory and Critical Care Medicine, The Second Affiliated Hospital of Medical College, Xi'an Jiaotong University, 157 West 5th Road, Xi'an, Shaanxi, China
| | - Yun Liu
- Department of Respiratory and Critical Care Medicine, The Second Affiliated Hospital of Medical College, Xi'an Jiaotong University, 157 West 5th Road, Xi'an, Shaanxi, China
| | - Nan Wang
- School of Pharmacy, Xi'an Jiaotong University, Xi'an, China.
| | - Yuanyuan Wu
- Department of Respiratory and Critical Care Medicine, The Second Affiliated Hospital of Medical College, Xi'an Jiaotong University, 157 West 5th Road, Xi'an, Shaanxi, China.
| |
Collapse
|
4
|
Roy MJ, Surudoi MG, Kropp A, Hou J, Dai W, Hardy JM, Liang LY, Cotton TR, Lechtenberg BC, Dite TA, Ma X, Daly RJ, Patel O, Lucet IS. Structural mapping of PEAK pseudokinase interactions identifies 14-3-3 as a molecular switch for PEAK3 signaling. Nat Commun 2023; 14:3542. [PMID: 37336884 DOI: 10.1038/s41467-023-38869-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2022] [Accepted: 05/16/2023] [Indexed: 06/21/2023] Open
Abstract
PEAK pseudokinases regulate cell migration, invasion and proliferation by recruiting key signaling proteins to the cytoskeleton. Despite lacking catalytic activity, alteration in their expression level is associated with several aggressive cancers. Here, we elucidate the molecular details of key PEAK signaling interactions with the adapter proteins CrkII and Grb2 and the scaffold protein 14-3-3. Our findings rationalize why the dimerization of PEAK proteins has a crucial function in signal transduction and provide biophysical and structural data to unravel binding specificity within the PEAK interactome. We identify a conserved high affinity 14-3-3 motif on PEAK3 and demonstrate its role as a molecular switch to regulate CrkII binding and signaling via Grb2. Together, our studies provide a detailed structural snapshot of PEAK interaction networks and further elucidate how PEAK proteins, especially PEAK3, act as dynamic scaffolds that exploit adapter proteins to control signal transduction in cell growth/motility and cancer.
Collapse
Affiliation(s)
- Michael J Roy
- The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC, 3052, Australia.
- Department of Medical Biology, University of Melbourne, Parkville, VIC, 3052, Australia.
| | - Minglyanna G Surudoi
- The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC, 3052, Australia
- Department of Medical Biology, University of Melbourne, Parkville, VIC, 3052, Australia
| | - Ashleigh Kropp
- The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC, 3052, Australia
- Department of Medical Biology, University of Melbourne, Parkville, VIC, 3052, Australia
| | - Jianmei Hou
- Cancer Program, Biomedicine Discovery Institute, Monash University, Melbourne, VIC, 3800, Australia
- Department of Biochemistry and Molecular Biology, Monash University, Melbourne, VIC, 3800, Australia
| | - Weiwen Dai
- The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC, 3052, Australia
- Department of Medical Biology, University of Melbourne, Parkville, VIC, 3052, Australia
| | - Joshua M Hardy
- The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC, 3052, Australia
- Department of Medical Biology, University of Melbourne, Parkville, VIC, 3052, Australia
| | - Lung-Yu Liang
- The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC, 3052, Australia
- Department of Medical Biology, University of Melbourne, Parkville, VIC, 3052, Australia
| | - Thomas R Cotton
- The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC, 3052, Australia
- Department of Medical Biology, University of Melbourne, Parkville, VIC, 3052, Australia
| | - Bernhard C Lechtenberg
- The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC, 3052, Australia
- Department of Medical Biology, University of Melbourne, Parkville, VIC, 3052, Australia
| | - Toby A Dite
- The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC, 3052, Australia
- Department of Medical Biology, University of Melbourne, Parkville, VIC, 3052, Australia
| | - Xiuquan Ma
- Cancer Program, Biomedicine Discovery Institute, Monash University, Melbourne, VIC, 3800, Australia
- Department of Biochemistry and Molecular Biology, Monash University, Melbourne, VIC, 3800, Australia
| | - Roger J Daly
- Cancer Program, Biomedicine Discovery Institute, Monash University, Melbourne, VIC, 3800, Australia
- Department of Biochemistry and Molecular Biology, Monash University, Melbourne, VIC, 3800, Australia
| | - Onisha Patel
- The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC, 3052, Australia
- Department of Medical Biology, University of Melbourne, Parkville, VIC, 3052, Australia
| | - Isabelle S Lucet
- The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC, 3052, Australia.
- Department of Medical Biology, University of Melbourne, Parkville, VIC, 3052, Australia.
| |
Collapse
|
5
|
Gasilina A, Yoon HY, Jian X, Luo R, Randazzo PA. A lysine-rich cluster in the N-BAR domain of ARF GTPase-activating protein ASAP1 is necessary for binding and bundling actin filaments. J Biol Chem 2022; 298:101700. [PMID: 35143843 PMCID: PMC8902617 DOI: 10.1016/j.jbc.2022.101700] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2021] [Revised: 01/25/2022] [Accepted: 01/28/2022] [Indexed: 12/05/2022] Open
Abstract
Actin filament maintenance is critical for both normal cell homeostasis and events associated with malignant transformation. The ADP-ribosylation factor GTPase-activating protein ASAP1 regulates the dynamics of filamentous actin-based structures, including stress fibers, focal adhesions, and circular dorsal ruffles. Here, we have examined the molecular basis for ASAP1 association with actin. Using a combination of structural modeling, mutagenesis, and in vitro and cell-based assays, we identify a putative-binding interface between the N-Bin-Amphiphysin-Rvs (BAR) domain of ASAP1 and actin filaments. We found that neutralization of charges and charge reversal at positions 75, 76, and 79 of ASAP1 reduced the binding of ASAP1 BAR-pleckstrin homology tandem to actin filaments and abrogated actin bundle formation in vitro. In addition, overexpression of actin-binding defective ASAP1 BAR-pleckstrin homology [K75, K76, K79] mutants prevented cellular actin remodeling in U2OS cells. Exogenous expression of [K75E, K76E, K79E] mutant of full-length ASAP1 did not rescue the reduction of cellular actin fibers consequent to knockdown of endogenous ASAP1. Taken together, our results support the hypothesis that the lysine-rich cluster in the N-BAR domain of ASAP1 is important for regulating actin filament organization.
Collapse
Affiliation(s)
- Anjelika Gasilina
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, USA; Department of Biochemistry and Molecular & Cellular Biology, Georgetown University Medical Center, Washington, District of Columbia, USA
| | - Hye-Young Yoon
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - Xiaoying Jian
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - Ruibai Luo
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - Paul A Randazzo
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, USA.
| |
Collapse
|
6
|
Schreiber C, Gruber A, Roßwag S, Saraswati S, Harkins S, Thiele W, Foroushani ZH, Munding N, Schmaus A, Rothley M, Dimmler A, Tanaka M, Garvalov BK, Sleeman JP. Loss of ASAP1 in the MMTV-PyMT model of luminal breast cancer activates AKT, accelerates tumorigenesis, and promotes metastasis. Cancer Lett 2022; 533:215600. [PMID: 35181478 DOI: 10.1016/j.canlet.2022.215600] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2021] [Revised: 02/10/2022] [Accepted: 02/11/2022] [Indexed: 12/31/2022]
Abstract
ASAP1 is a multi-domain adaptor protein that regulates cytoskeletal dynamics, receptor recycling and intracellular vesicle trafficking. Its expression is associated with poor prognosis in a variety of cancers, and can promote cell migration, invasion and metastasis. Although amplification and expression of ASAP1 has been associated with poor survival in breast cancer, we found that in the autochthonous MMTV-PyMT model of luminal breast cancer, ablation of ASAP1 resulted in an earlier onset of tumor initiation and increased metastasis. This was due to tumor cell-intrinsic effects of ASAP1 deletion, as ASAP1 deficiency in tumor, but not in stromal cells was sufficient to replicate the enhanced tumorigenicity and metastasis observed in the ASAP1-null MMTV-PyMT mice. Loss of ASAP1 in MMTV-PyMT mice had no effect on proliferation, apoptosis, angiogenesis or immune cell infiltration, but enhanced mammary gland hyperplasia and tumor cell invasion, indicating that ASAP1 can accelerate tumor initiation and promote dissemination. Mechanistically, these effects were associated with a potent activation of AKT. Importantly, lower ASAP1 levels correlated with poor prognosis and enhanced AKT activation in human ER+/luminal breast tumors, validating our findings in the MMTV-PyMT mouse model for this subtype of breast cancer. Taken together, our findings reveal that ASAP1 can have distinct functions in different tumor types and demonstrate a tumor suppressive activity for ASAP1 in luminal breast cancer.
Collapse
Affiliation(s)
- Caroline Schreiber
- European Center for Angioscience (ECAS), Medical Faculty Mannheim, Heidelberg University, 68167, Mannheim, Germany
| | - Annette Gruber
- European Center for Angioscience (ECAS), Medical Faculty Mannheim, Heidelberg University, 68167, Mannheim, Germany
| | - Sven Roßwag
- European Center for Angioscience (ECAS), Medical Faculty Mannheim, Heidelberg University, 68167, Mannheim, Germany
| | - Supriya Saraswati
- European Center for Angioscience (ECAS), Medical Faculty Mannheim, Heidelberg University, 68167, Mannheim, Germany
| | - Shannon Harkins
- European Center for Angioscience (ECAS), Medical Faculty Mannheim, Heidelberg University, 68167, Mannheim, Germany
| | - Wilko Thiele
- European Center for Angioscience (ECAS), Medical Faculty Mannheim, Heidelberg University, 68167, Mannheim, Germany; Institute for Biological and Chemical Systems - Biological Information Processing (IBCS-BIP), Karlsruhe Institute of Technology (KIT) Campus North, D-76344 Karlsruhe, Germany
| | - Zahra Hajian Foroushani
- Physical Chemistry of Biosystems, Institute of Physical Chemistry, Heidelberg University, 69120, Heidelberg, Germany
| | - Natalie Munding
- Physical Chemistry of Biosystems, Institute of Physical Chemistry, Heidelberg University, 69120, Heidelberg, Germany
| | - Anja Schmaus
- European Center for Angioscience (ECAS), Medical Faculty Mannheim, Heidelberg University, 68167, Mannheim, Germany; Institute for Biological and Chemical Systems - Biological Information Processing (IBCS-BIP), Karlsruhe Institute of Technology (KIT) Campus North, D-76344 Karlsruhe, Germany
| | - Melanie Rothley
- European Center for Angioscience (ECAS), Medical Faculty Mannheim, Heidelberg University, 68167, Mannheim, Germany; Institute for Biological and Chemical Systems - Biological Information Processing (IBCS-BIP), Karlsruhe Institute of Technology (KIT) Campus North, D-76344 Karlsruhe, Germany
| | - Arno Dimmler
- Vincentius-Diakonissen-Kliniken, 76135, Karlsruhe, Germany
| | - Motomu Tanaka
- Physical Chemistry of Biosystems, Institute of Physical Chemistry, Heidelberg University, 69120, Heidelberg, Germany; Center for Integrative Medicine and Physics, Institute for Advanced Study, Kyoto University, 606-8501, Kyoto, Japan
| | - Boyan K Garvalov
- European Center for Angioscience (ECAS), Medical Faculty Mannheim, Heidelberg University, 68167, Mannheim, Germany.
| | - Jonathan P Sleeman
- European Center for Angioscience (ECAS), Medical Faculty Mannheim, Heidelberg University, 68167, Mannheim, Germany; Institute for Biological and Chemical Systems - Biological Information Processing (IBCS-BIP), Karlsruhe Institute of Technology (KIT) Campus North, D-76344 Karlsruhe, Germany.
| |
Collapse
|
7
|
ASAP1 regulates the uptake of Mycobacterium tuberculosis H37Ra in THP1-derived macrophages by remodeling actin cytoskeleton. Tuberculosis (Edinb) 2021; 129:102090. [PMID: 34058694 DOI: 10.1016/j.tube.2021.102090] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2020] [Revised: 04/02/2021] [Accepted: 05/16/2021] [Indexed: 11/23/2022]
Abstract
Tuberculosis is initiated by the entry of Mycobacterium tuberculosis (Mtb) into macrophages in the lungs. A study of the cellular factors responsible for the entry of Mtb into host cells will potentially benefit the development of therapeutic treatments or preventive agents against Mtb infection. Using human THP1-derived macrophages as a model, we found that infection of Mtb H37Ra transiently reduced the level of ASAP1, an ADP ribosylation factor (Arf)-GTPase activating protein. Furthermore, knockdown of ASAP1 increased the efficiency of H37Ra entry into the cell and altered the status of actin remodeling as indicated by the enhanced aggregation of F-actin and the increased numbers of vinculin- and paxillin-rich puncta. Collectively, the results in this report identified ASAP1 as a regulator controlling the entry of Mtb H37Ra into macrophage by remodeling actin cytoskeleton.
Collapse
|
8
|
ADP ribosylation factor guanylate kinase 1 promotes the malignant phenotype of gastric cancer by regulating focal adhesion kinase activation. Life Sci 2021; 273:119264. [PMID: 33639150 DOI: 10.1016/j.lfs.2021.119264] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Revised: 02/11/2021] [Accepted: 02/16/2021] [Indexed: 11/21/2022]
Abstract
AIMS ADP ribosylation factor guanylate kinase 1 (ASAP1), a phospholipid-dependent guanosine triphosphate (GTP)ase activating protein, has been reported to be involved in the development of various malignant tumors. However, the biological function of ASAP1 in gastric cancer (GC) remains unclear. This study was to investigate its effect and the underlying mechanism for the malignant phenotype of GC. MATERIALS AND METHODS The Cell Counting Kit-8 assay, flow cytometry, Transwell invasion assay, and wound-healing assay were used to assess the malignant biological behavior of GC cells with ASAP1 overexpression and knockdown. In addition, co-immunoprecipitation was used to analyze the interaction between ASAP1 and FAK in BGC823 cells, and western blotting was used to determine the effects of overexpression and knockdown of ASAP1 on FAK activity in BGC823 cells. Subsequently, functional recovery experiments were used to observe the effect of ASAP1 and FAK on the malignant phenotype of GC cells. KEY FINDINGS ASAP1 overexpression strongly promoted the malignant biological behavior of SGC7901 cells. Knockdown of ASAP1 effectively weakened the malignant biological behavior of SGC7901 and BGC823 cells. ASAP1 directly interacted with FAK to potentiate FAK activation. In addition, knockdown of FAK combined with ASAP1 overexpression significantly weakened the malignant biological behavior of GC cells, whereas overexpression of FAK combined with knockdown of ASAP1 significantly enhanced the malignant biological behavior of GC cells. SIGNIFICANCE ASAP1 interacted with FAK, and ASAP1 promoted the malignant phenotype of GC cells by regulating FAK activity. The specific underlying mechanism is worth further investigation.
Collapse
|
9
|
Chen PW, Billington N, Maron BY, Sload JA, Chinthalapudi K, Heissler SM. The BAR domain of the Arf GTPase-activating protein ASAP1 directly binds actin filaments. J Biol Chem 2020; 295:11303-11315. [PMID: 32444496 DOI: 10.1074/jbc.ra119.009903] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2019] [Revised: 05/13/2020] [Indexed: 12/11/2022] Open
Abstract
The Arf GTPase-activating protein (Arf GAP) with SH3 domain, ankyrin repeat and PH domain 1 (ASAP1) establishes a connection between the cell membrane and the cortical actin cytoskeleton. The formation, maintenance, and turnover of actin filaments and bundles in the actin cortex are important for cell adhesion, invasion, and migration. Here, using actin cosedimentation, polymerization, and depolymerization assays, along with total internal reflection fluorescence (TIRF), confocal, and EM analyses, we show that the N-terminal N-BAR domain of ASAP1 directly binds to F-actin. We found that ASAP1 homodimerization aligns F-actin in predominantly unipolar bundles and stabilizes them against depolymerization. Furthermore, the ASAP1 N-BAR domain moderately reduced the spontaneous polymerization of G-actin. The overexpression of the ASAP1 BAR-PH tandem domain in fibroblasts induced the formation of actin-filled projections more effectively than did full-length ASAP1. An ASAP1 construct that lacked the N-BAR domain failed to induce cellular projections. Our results suggest that ASAP1 regulates the dynamics and the formation of higher-order actin structures, possibly through direct binding to F-actin via its N-BAR domain. We propose that ASAP1 is a hub protein for dynamic protein-protein interactions in mechanosensitive structures, such as focal adhesions, invadopodia, and podosomes, that are directly implicated in oncogenic events. The effect of ASAP1 on actin dynamics puts a spotlight on its function as a central signaling molecule that regulates the dynamics of the actin cytoskeleton by transmitting signals from the plasma membrane.
Collapse
Affiliation(s)
- Pei-Wen Chen
- Department of Biology, Williams College, Williamstown, Massachusetts, USA
| | - Neil Billington
- Laboratory of Molecular Physiology, National Heart, Lung, and Blood Institute, Bethesda, Maryland, USA
| | - Ben Y Maron
- Department of Biology, Williams College, Williamstown, Massachusetts, USA
| | - Jeffrey A Sload
- Department of Biology, Williams College, Williamstown, Massachusetts, USA
| | - Krishna Chinthalapudi
- Department of Physiology and Cell Biology, Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, Ohio, USA
| | - Sarah M Heissler
- Department of Physiology and Cell Biology, Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, Ohio, USA
| |
Collapse
|
10
|
Luo Q, Zhang S, Zhang D, Yuan F, Chen X, Yang S. Expression of ASAP1 and FAK in gastric cancer and its clinicopathological significance. Oncol Lett 2020; 20:974-980. [PMID: 32566028 DOI: 10.3892/ol.2020.11612] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2019] [Accepted: 03/06/2020] [Indexed: 01/23/2023] Open
Abstract
The present study aimed to analyze the expression levels of adenosine diphosphate ribosylation factor guanylate kinase 1 (ASAP1) and focal adhesion kinase (FAK) in gastric cancer (GC) tissues in order to explore their association with clinicopathological features and prognosis. A total of 32 patients with GC were enrolled in the present study. All patients had complete clinical follow-up data and paraffin-embedded normal gastric mucosal tissues. The expression levels of ASAP1 and FAK in these tissues were measured by immunohistochemistry. The associations of ASAP1 and FAK expression with clinicopathological factors and the survival of patients with GC were subsequently analyzed. The expression levels of ASAP1 (59.4%) and FAK (68.8%) in GC tissues were significantly higher than those in normal gastric mucosal tissues (28.1 and 40.6%, P<0.05). The expression levels of ASAP1 and FAK were associated with depth of invasion, lymph node metastasis and pathological stage (P<0.05). ASAP1 expression was positively associated with FAK expression (P<0.001). In addition, ASAP1 and FAK expression levels were negatively associated with disease-free survival time and overall survival time (P<0.05). The 5-year overall survival rate was significantly higher in patients with negative ASAP1 or FAK expression compared with that in patients with positive ASAP1 or FAK expression (P<0.05). In conclusion, ASAP1 and FAK were highly expressed in human GC tissues and may serve a synergistic role in promoting tumorigenesis, progression, invasion and metastasis in patients with GC. ASAP1 and FAK expression in GC were associated with patient's survival. Therefore, ASAP1 and FAK may represent novel molecular markers for the pathophysiology and prognosis of GC.
Collapse
Affiliation(s)
- Qiong Luo
- Department of Oncology Medicine, Fujian Medical University Union Hospital, Fuzhou, Fujian 350001, P.R. China
| | - Suyun Zhang
- Department of Oncology Medicine, Fujian Medical University Union Hospital, Fuzhou, Fujian 350001, P.R. China
| | - Donghuan Zhang
- Department of Oncology Medicine, Fujian Medical University Union Hospital, Fuzhou, Fujian 350001, P.R. China
| | - Fang Yuan
- Department of Respiratory Medicine, Fujian Medical University Union Hospital, Fuzhou, Fujian 350001, P.R. China
| | - Xiangqi Chen
- Department of Respiratory Medicine, Fujian Medical University Union Hospital, Fuzhou, Fujian 350001, P.R. China
| | - Sheng Yang
- Department of Oncology Medicine, Fujian Medical University Union Hospital, Fuzhou, Fujian 350001, P.R. China
| |
Collapse
|
11
|
Gasilina A, Vitali T, Luo R, Jian X, Randazzo PA. The ArfGAP ASAP1 Controls Actin Stress Fiber Organization via Its N-BAR Domain. iScience 2019; 22:166-180. [PMID: 31785555 PMCID: PMC6889188 DOI: 10.1016/j.isci.2019.11.015] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Revised: 09/30/2019] [Accepted: 11/06/2019] [Indexed: 12/11/2022] Open
Abstract
ASAP1 is a multi-domain ArfGAP that controls cell migration, spreading, and focal adhesion dynamics. Although its GAP activity contributes to remodeling of the actin cytoskeleton, it does not fully explain all cellular functions of ASAP1. Here we find that ASAP1 regulates actin filament assembly directly through its N-BAR domain and controls stress fiber maintenance. ASAP1 depletion caused defects in stress fiber organization. Conversely, overexpression of ASAP1 enhanced actin remodeling. The BAR-PH fragment was sufficient to affect actin. ASAP1 with the BAR domain replaced with the BAR domain of the related ACAP1 did not affect actin. The BAR-PH tandem of ASAP1 bound and bundled actin filaments directly, whereas the presence of the ArfGAP and the C-terminal linker/SH3 domain reduced binding and bundling of filaments by BAR-PH. Together these data provide evidence that ASAP1 may regulate the actin cytoskeleton through direct interaction of the BAR-PH domain with actin filaments.
Collapse
Affiliation(s)
- Anjelika Gasilina
- Section on Regulation of Ras Superfamily, Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bldg. 37, Rm. 2042, Bethesda, MD 20892, USA; Department of Biochemistry and Molecular & Cellular Biology, Georgetown University Medical Center, Washington, DC 20007, USA
| | - Teresa Vitali
- Section on Regulation of Ras Superfamily, Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bldg. 37, Rm. 2042, Bethesda, MD 20892, USA
| | - Ruibai Luo
- Section on Regulation of Ras Superfamily, Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bldg. 37, Rm. 2042, Bethesda, MD 20892, USA
| | - Xiaoying Jian
- Section on Regulation of Ras Superfamily, Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bldg. 37, Rm. 2042, Bethesda, MD 20892, USA
| | - Paul A Randazzo
- Section on Regulation of Ras Superfamily, Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bldg. 37, Rm. 2042, Bethesda, MD 20892, USA.
| |
Collapse
|
12
|
Tanna CE, Goss LB, Ludwig CG, Chen PW. Arf GAPs as Regulators of the Actin Cytoskeleton-An Update. Int J Mol Sci 2019; 20:ijms20020442. [PMID: 30669557 PMCID: PMC6358971 DOI: 10.3390/ijms20020442] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2018] [Revised: 01/14/2019] [Accepted: 01/15/2019] [Indexed: 12/25/2022] Open
Abstract
Arf GTPase-activating proteins (Arf GAPs) control the activity of ADP-ribosylation factors (Arfs) by inducing GTP hydrolysis and participate in a diverse array of cellular functions both through mechanisms that are dependent on and independent of their Arf GAP activity. A number of these functions hinge on the remodeling of actin filaments. Accordingly, some of the effects exerted by Arf GAPs involve proteins known to engage in regulation of the actin dynamics and architecture, such as Rho family proteins and nonmuscle myosin 2. Circular dorsal ruffles (CDRs), podosomes, invadopodia, lamellipodia, stress fibers and focal adhesions are among the actin-based structures regulated by Arf GAPs. Arf GAPs are thus important actors in broad functions like adhesion and motility, as well as the specialized functions of bone resorption, neurite outgrowth, and pathogen internalization by immune cells. Arf GAPs, with their multiple protein-protein interactions, membrane-binding domains and sites for post-translational modification, are good candidates for linking the changes in actin to the membrane. The findings discussed depict a family of proteins with a critical role in regulating actin dynamics to enable proper cell function.
Collapse
Affiliation(s)
- Christine E Tanna
- Department of Biology, Williams College, Williamstown, MA 01267, USA.
| | - Louisa B Goss
- Department of Biology, Williams College, Williamstown, MA 01267, USA.
| | - Calvin G Ludwig
- Department of Biology, Williams College, Williamstown, MA 01267, USA.
| | - Pei-Wen Chen
- Department of Biology, Williams College, Williamstown, MA 01267, USA.
| |
Collapse
|
13
|
Luo R, Chen PW, Kuo JC, Jenkins L, Jian X, Waterman CM, Randazzo PA. ARAP2 inhibits Akt independently of its effects on focal adhesions. Biol Cell 2018; 110:257-270. [PMID: 30144359 DOI: 10.1111/boc.201800044] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2018] [Accepted: 08/17/2018] [Indexed: 12/15/2022]
Abstract
BACKGROUND INFORMATION ARAP2, an Arf GTPase-activating protein (Arf GAP) that binds to adaptor protein with PH domain, PTB domain and leucine zipper motifs 1 (APPL1), regulates focal adhesions (FAs). APPL1 affects FA dynamics by regulating Akt. Here, we tested the hypothesis that ARAP2 affects FAs in part by regulating Akt through APPL1. RESULTS We found that ARAP2 controlled FA dynamics dependent on its enzymatic Arf GAP activity. In some cells, ARAP2 also regulated phosphoAkt (pAkt) levels. However, ARAP2 control of FAs did not require Akt and conversely, the effects on pAkt were independent of FAs. Reducing ARAP2 expression reduced the size and number of FAs in U118, HeLa and MDA-MB-231 cells. Decreasing ARAP2 expression increased pAkt in U118 cells and HeLa cells and overexpressing ARAP2 decreased pAkt in U118 cells; in contrast, ARAP2 had no effect on pAkt in MDA-MB-231 cells. An Akt inhibitor did not block the effect of reduced ARAP2 on FAs in U118. Furthermore, the effect of ARAP2 on Akt did not require Arf GAP activity, which is necessary for effects on FAs and integrin traffic. Altering FAs by other means did not induce the same changes in pAkt as those seen by reducing ARAP2 in U118 cells. In addition, we discovered that ARAP2 and APPL1 had co-ordinated effects on pAkt in U118 cells. Reduced APPL1 expression, as for ARAP2, increased pAkt in U118 and the effect of reduced APPL1 expression was reversed by overexpressing ARAP2. Conversely, the effect of reduced ARAP2 expression was reversed by overexpressing APPL1. ARAP2 is an Arf GAP that has previously been reported to affect FAs by regulating Arf6 and integrin trafficking and to bind to the adaptor proteins APPL1. Here, we report that ARAP2 suppresses pAkt levels in cells co-ordinately with APPL1 and independently of GAP activity and its effect on the dynamic behaviour of FAs. CONCLUSIONS We conclude that ARAP2 affects Akt signalling in some cells by a mechanism independent of FAs or membrane traffic. SIGNIFICANCE Our results highlight an Arf GAP-independent function of ARAP2 in regulating Akt activity and distinguish the effect of ARAP2 on Akt from that on FAs and integrin trafficking, which requires regulation of Arf6.
Collapse
Affiliation(s)
- Ruibai Luo
- Laboratory of Cellular and Molecular Biology, National Cancer Institute, Bethesda, MD, 20892, USA
| | - Pei-Wen Chen
- Laboratory of Cellular and Molecular Biology, National Cancer Institute, Bethesda, MD, 20892, USA.,Department of Biology, Williams College, Williamstown, MA, 01267, USA
| | - Jean-Cheng Kuo
- Cell Biology and Physiology Center, National Heart, Lung, and Blood Institutes, Bethesda, MD, 20892, USA.,Institute of Biochemistry and Molecular Biology, National Yang-Ming University, Taipei, 112, Taiwan
| | - Lisa Jenkins
- Laboratory of Cell Biology, National Cancer Institute, Bethesda, MD, 20892, USA
| | - Xiaoying Jian
- Laboratory of Cellular and Molecular Biology, National Cancer Institute, Bethesda, MD, 20892, USA
| | - Clare M Waterman
- Cell Biology and Physiology Center, National Heart, Lung, and Blood Institutes, Bethesda, MD, 20892, USA
| | - Paul A Randazzo
- Laboratory of Cellular and Molecular Biology, National Cancer Institute, Bethesda, MD, 20892, USA
| |
Collapse
|
14
|
eIF5B increases ASAP1 expression to promote HCC proliferation and invasion. Oncotarget 2018; 7:62327-62339. [PMID: 27694689 PMCID: PMC5308730 DOI: 10.18632/oncotarget.11469] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2016] [Accepted: 08/09/2016] [Indexed: 12/19/2022] Open
Abstract
Hepatocellular carcinoma (HCC) is the third most common cause of cancer-related death worldwide. Despite the therapeutic advances that have been achieved during the past decade, the molecular pathogenesis underlying HCC remains poorly understood. In this study, we discovered that increased expression eukaryotic translation initiation factor 5B (eIF5B) was significantly correlated with aggressive characteristics and associated with shorter recurrence-free survival (RFS) and overall survival (OS) in a large cohort. We also found that eIF5B promoted HCC cell proliferation and migration in vitro and in vivo partly through increasing ASAP1 expression. Our findings strongly suggested that eIF5B could promote HCC progression and be considered a prognostic biomarker for HCC.
Collapse
|
15
|
Wang X, Ma A, Han X, Litifu A, Xue F. ASAP1 gene polymorphisms are associated with susceptibility to tuberculosis in a Chinese Xinjiang Muslim population. Exp Ther Med 2018; 15:3392-3398. [PMID: 29545860 PMCID: PMC5841074 DOI: 10.3892/etm.2018.5800] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2017] [Accepted: 01/10/2018] [Indexed: 01/14/2023] Open
Abstract
Seven single-nucleotide polymorphism (SNP) sites located in ASAP1 gene have been found associated with tuberculosis (TB) susceptibility by genome-wide association studies in Russia. The case-control study was carried out to test whether these seven SNPs were associated with susceptibility to TB in a Chinese Xinjiang Muslim population. The seven SNPs were genotyped in a case-control design that included 780 Xinjiang Muslim subjects (400 TB patients and 380 controls). Multiplex PCR and direct sequencing were used to detect ASAP1 gene polymorphisms. Hardy-Weinberg equilibrium test was performed to test whether the sample was from genetic equilibrium population. The associations of SNPs with TB risk were determined by the distributions of allelic frequencies and different genetic models. Significant differences of the allelic distribution of rs4733781 and rs1017281 in ASAP1 gene were observed between control group and TB group. A allele of rs4733781 was associated with TB risk (TB vs. control, OR=1.242; 95% CI: 1.004-1.537, P=0.046); While in rs1017281 site, G allele was associated with increased risk for TB (TB vs. control, OR: 0.792, 95% CI: 0.643-0.976, P=0.028). The recessive model of rs4733781 (CC vs. AC+AA) in Xinjiang Muslim populations was associated with a lower TB risk [P=0.003, OR=0.51 (0.324-0.802)], while the recessive model of rs1017281 (GG vs. AG+AA) was associated with a higher TB risk [P=0.011, OR=1.792 (1.135-2.828)]. Using case-control analysis, we identified that two genetic polymorphism sites in the ASAP1 relate to host susceptibility of TB in a Chinese Xinjiang Muslim population.
Collapse
Affiliation(s)
- Xianhua Wang
- The School of Public Health, Qingdao University Medical College, Qingdao, Shandong 266021, P.R. China
| | - Aiguo Ma
- The School of Public Health, Qingdao University Medical College, Qingdao, Shandong 266021, P.R. China
| | - Xiuxia Han
- The School of Public Health, Qingdao University Medical College, Qingdao, Shandong 266021, P.R. China
| | - Aishan Litifu
- Department of Respiratory Medicine, Xinjiang Uygur Autonomous Region Chest Hospital, Urumqi, Xinjiang, 830049, P.R. China
| | - Feng Xue
- Department of Tuberculosis, Xinjiang Uygur Autonomous Region Center for Disease Control and Prevention, Xinjiang Uygur Autonomous Region, Urumqi, Xinjiang 830001, P.R. China
| |
Collapse
|
16
|
Abstract
PURPOSE OF REVIEW Although platelet endocytosis has been recognized in granule cargo loading and the trafficking of several platelet surface receptors, its acute physiological relevance is poorly understood as is its mechanism. The present review discusses the current understanding of platelet endocytosis and its implications for platelet function. RECENT FINDINGS Recent studies are beginning to identify and define the proteins that mediate platelet endocytosis. These studies have shown that platelets contain different endosomal compartments and may use multiple endocytic routes to take in circulating molecules and surface proteins. The studies have also shown that platelet endocytosis is involved in several aspects of platelet function such as signaling, spreading, and granule cargo loading. SUMMARY Mechanistic studies of platelet endocytosis have shown it to be not only involved in granule cargo loading but also in various other platelet functions important for hemostasis and beyond.
Collapse
|
17
|
Luo R, Reed CE, Sload JA, Wordeman L, Randazzo PA, Chen PW. Arf GAPs and molecular motors. Small GTPases 2017; 10:196-209. [PMID: 28430047 DOI: 10.1080/21541248.2017.1308850] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Arf GTPase-activating proteins (Arf GAPs) were first identified as regulators of the small GTP-binding proteins ADP-ribosylation factors (Arfs). The Arf GAPs are a large family of proteins in metazoans, outnumbering the Arfs that they regulate. The members of the Arf GAP family have complex domain structures and some have been implicated in particular cellular functions, such as cell migration, or with particular pathologies, such as tumor invasion and metastasis. The specific effects of Arfs sometimes depend on the Arf GAP involved in their regulation. These observations have led to speculation that the Arf GAPs themselves may affect cellular activities in capacities beyond the regulation of Arfs. Recently, 2 Arf GAPs, ASAP1 and AGAP1, have been found to bind directly to and influence the activity of myosins and kinesins, motor proteins associated with filamentous actin and microtubules, respectively. The Arf GAP-motor protein interaction is critical for cellular behaviors involving the actin cytoskeleton and microtubules, such as cell migration and other cell movements. Arfs, then, may function with molecular motors through Arf GAPs to regulate microtubule and actin remodeling.
Collapse
Affiliation(s)
- Ruibai Luo
- a Laboratory of Cellular and Molecular Biology , National Cancer Institute, National Institutes of Health , Bethesda , MD , USA
| | - Christine E Reed
- c Department of Biology , Williams College , Williamstown , MA , USA
| | - Jeffrey A Sload
- c Department of Biology , Williams College , Williamstown , MA , USA
| | - Linda Wordeman
- b Department of Physiology and Biophysics , University of Washington School of Medicine , Seattle , WA , USA
| | - Paul A Randazzo
- a Laboratory of Cellular and Molecular Biology , National Cancer Institute, National Institutes of Health , Bethesda , MD , USA
| | - Pei-Wen Chen
- c Department of Biology , Williams College , Williamstown , MA , USA
| |
Collapse
|
18
|
Bauer J, Kopp S, Schlagberger EM, Grosse J, Sahana J, Riwaldt S, Wehland M, Luetzenberg R, Infanger M, Grimm D. Proteome Analysis of Human Follicular Thyroid Cancer Cells Exposed to the Random Positioning Machine. Int J Mol Sci 2017; 18:ijms18030546. [PMID: 28273809 PMCID: PMC5372562 DOI: 10.3390/ijms18030546] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2016] [Revised: 02/27/2017] [Accepted: 02/27/2017] [Indexed: 01/13/2023] Open
Abstract
Several years ago, we detected the formation of multicellular spheroids in experiments with human thyroid cancer cells cultured on the Random Positioning Machine (RPM), a ground-based model to simulate microgravity by continuously changing the orientation of samples. Since then, we have studied cellular mechanisms triggering the cells to leave a monolayer and aggregate to spheroids. Our work focused on spheroid-related changes in gene expression patterns, in protein concentrations, and in factors secreted to the culture supernatant during the period when growth is altered. We detected that factors inducing angiogenesis, the composition of integrins, the density of the cell monolayer exposed to microgravity, the enhanced production of caveolin-1, and the nuclear factor kappa B p65 could play a role during spheroid formation in thyroid cancer cells. In this study, we performed a deep proteome analysis on FTC-133 thyroid cancer cells cultured under conditions designed to encourage or discourage spheroid formation. The experiments revealed more than 5900 proteins. Their evaluation confirmed and explained the observations mentioned above. In addition, we learned that FTC-133 cells growing in monolayers or in spheroids after RPM-exposure incorporate vinculin, paxillin, focal adhesion kinase 1, and adenine diphosphate (ADP)-ribosylation factor 6 in different ways into the focal adhesion complex.
Collapse
Affiliation(s)
- Johann Bauer
- Max-Planck-Institute for Biochemistry, Scientific Information Services, 82152 Martinsried, Germany.
| | - Sascha Kopp
- Clinic and Policlinic for Plastic, Aesthetic and Hand Surgery, Otto-von-Guericke-University, 39120 Magdeburg, Germany.
| | | | - Jirka Grosse
- Department of Nuclear Medicine, University Hospital, University of Regensburg, 95053 Regensburg, Germany.
| | - Jayashree Sahana
- Department of Biomedicine, Aarhus University, 8000 Aarhus C, Denmark.
| | - Stefan Riwaldt
- Department of Biomedicine, Aarhus University, 8000 Aarhus C, Denmark.
| | - Markus Wehland
- Clinic and Policlinic for Plastic, Aesthetic and Hand Surgery, Otto-von-Guericke-University, 39120 Magdeburg, Germany.
| | - Ronald Luetzenberg
- Clinic and Policlinic for Plastic, Aesthetic and Hand Surgery, Otto-von-Guericke-University, 39120 Magdeburg, Germany.
| | - Manfred Infanger
- Clinic and Policlinic for Plastic, Aesthetic and Hand Surgery, Otto-von-Guericke-University, 39120 Magdeburg, Germany.
| | - Daniela Grimm
- Clinic and Policlinic for Plastic, Aesthetic and Hand Surgery, Otto-von-Guericke-University, 39120 Magdeburg, Germany.
- Department of Biomedicine, Aarhus University, 8000 Aarhus C, Denmark.
| |
Collapse
|
19
|
Benz PM, Laban H, Zink J, Günther L, Walter U, Gambaryan S, Dib K. Vasodilator-Stimulated Phosphoprotein (VASP)-dependent and -independent pathways regulate thrombin-induced activation of Rap1b in platelets. Cell Commun Signal 2016; 14:21. [PMID: 27620165 PMCID: PMC5020514 DOI: 10.1186/s12964-016-0144-z] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2016] [Accepted: 09/06/2016] [Indexed: 11/13/2022] Open
Abstract
Background Vasodilator-Stimulated Phosphoprotein (VASP) is involved in the inhibition of agonist-induced platelet aggregation by cyclic nucleotides and the adhesion of platelets to the vascular wall. αIIbβ3 is the main integrin responsible for platelet activation and Rap1b plays a key role in integrin signalling. We investigated whether VASP is involved in the regulation of Rap1b in platelets since VASP-null platelets exhibit augmented adhesion to endothelial cells in vivo. Methods Washed platelets from wild type and VASP-deficient mice were stimulated with thrombin, the purinergic receptors agonist ADP, or the thromboxane A2 receptor agonist U46619 and Rap1b activation was measured using the GST-RalGDS-RBD binding assay. Interaction of VASP and Crkl was investigated by co-immunoprecipitation, confocal microscopy, and pull-down assays using Crkl domains expressed as GST-fusion proteins. Results Surprisingly, we found that activation of Rap1b in response to thrombin, ADP, or U46619 was significantly reduced in platelets from VASP-null mice compared to platelets from wild type mice. However, inhibition of thrombin-induced activation of Rap1b by nitric oxide (NO) was similar in platelets from wild type and VASP-null mice indicating that the NO/cGMP/PKG pathway controls inhibition of Rap1b independently from VASP. To understand how VASP regulated Rap1b, we investigated association between VASP and the Crk-like protein (Crkl), an adapter protein which activates the Rap1b guanine nucleotide exchange factor C3G. We demonstrated the formation of a Crkl/VASP complex by showing that: 1) Crkl co-immunoprecipitated VASP from platelet lysates; 2) Crkl and VASP dynamically co-localized at actin-rich protrusions reminiscent of focal adhesions, filopodia, and lamellipodia upon platelet spreading on fibronectin; 3) recombinant VASP bound directly to the N-terminal SH3 domain of Crkl; 4) Protein Kinase A (PKA) -mediated VASP phosphorylation on Ser157 abrogated the binding of Crkl. Conclusions We identified Crkl as a novel protein interacting with VASP in platelets. We propose that the C3G/Crkl/VASP complex plays a role in the regulation of Rap1b and this explains, at least in part, the reduced agonist-induced activation of Rap1b in VASP-null platelets. In addition, the fact that PKA-dependent VASP phosphorylation abrogated its interaction with Crkl may provide, at least in part, a rationale for the PKA-dependent inhibition of Rap1b and platelet aggregation.
Collapse
Affiliation(s)
- Peter M Benz
- Institute for Vascular Signalling, Centre for Molecular Medicine, Johann Wolfgang Goethe University and DZHK (German Centre for Cardiovascular Research) partner site Rhine-Main, 60590, Frankfurt, Germany
| | - Hebatullah Laban
- Institute for Vascular Signalling, Centre for Molecular Medicine, Johann Wolfgang Goethe University and DZHK (German Centre for Cardiovascular Research) partner site Rhine-Main, 60590, Frankfurt, Germany
| | - Joana Zink
- Institute for Vascular Signalling, Centre for Molecular Medicine, Johann Wolfgang Goethe University and DZHK (German Centre for Cardiovascular Research) partner site Rhine-Main, 60590, Frankfurt, Germany
| | - Lea Günther
- Institute for Vascular Signalling, Centre for Molecular Medicine, Johann Wolfgang Goethe University and DZHK (German Centre for Cardiovascular Research) partner site Rhine-Main, 60590, Frankfurt, Germany
| | - Ulrich Walter
- Centre for Thrombosis and Hemostasis (CTH), University Medical Center Mainz, Mainz, Germany
| | - Stepan Gambaryan
- Department of Cytology and Histology, St. Petersburg State University, St. Petersburg, Russia.,Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, St. Petersburg, Russia
| | - Karim Dib
- Centre for Experimental Medicine, Medical Biology Center (MBC) building, Queen's University of Belfast, Third floor, 97 Lisburn Road, BT9 7BL, Belfast, Northern Ireland, UK.
| |
Collapse
|
20
|
Roy NS, Yohe ME, Randazzo PA, Gruschus JM. Allosteric properties of PH domains in Arf regulatory proteins. CELLULAR LOGISTICS 2016; 6:e1181700. [PMID: 27294009 DOI: 10.1080/21592799.2016.1181700] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/2016] [Revised: 04/13/2016] [Accepted: 04/14/2016] [Indexed: 10/21/2022]
Abstract
Pleckstrin Homology (PH) domains bind phospholipids and proteins. They are critical regulatory elements of a number enzymes including guanine nucleotide exchange factors (GEFs) and GTPase-activating proteins (GAPs) for Ras-superfamily guanine nucleotide binding proteins such as ADP-ribosylation factors (Arfs). Recent studies have indicated that many PH domains may bind more than one ligand cooperatively. Here we discuss the molecular basis of PH domain-dependent allosteric behavior of 2 ADP-ribosylation factor exchange factors, Grp1 and Brag2, cooperative binding of ligands to the PH domains of Grp1 and the Arf GTPase-activating protein, ASAP1, and the consequences for activity of the associated catalytic domains.
Collapse
Affiliation(s)
- Neeladri Sekhar Roy
- Laboratory of Cellular and Molecular Biology, National Cancer Institute, National Institutes of Health , Bethesda, MD, USA
| | - Marielle E Yohe
- Genetics Branch, National Cancer Institute, National Institutes of Health , Bethesda, MD, USA
| | - Paul A Randazzo
- Laboratory of Cellular and Molecular Biology, National Cancer Institute, National Institutes of Health , Bethesda, MD, USA
| | - James M Gruschus
- Laboratory of Structural Biophysics, National Heart, Lung and Blood Institute, National Institutes of Health , Bethesda, MD, USA
| |
Collapse
|
21
|
Chen PW, Jian X, Heissler SM, Le K, Luo R, Jenkins LM, Nagy A, Moss J, Sellers JR, Randazzo PA. The Arf GTPase-activating Protein, ASAP1, Binds Nonmuscle Myosin 2A to Control Remodeling of the Actomyosin Network. J Biol Chem 2016; 291:7517-26. [PMID: 26893376 DOI: 10.1074/jbc.m115.701292] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2015] [Indexed: 01/13/2023] Open
Abstract
ASAP1 regulates F-actin-based structures and functions, including focal adhesions (FAs) and circular dorsal ruffles (CDRs), cell spreading and migration. ASAP1 function requires its N-terminal BAR domain. We discovered that nonmuscle myosin 2A (NM2A) directly bound the BAR-PH tandem of ASAP1in vitro ASAP1 and NM2A co-immunoprecipitated and colocalized in cells. Knockdown of ASAP1 reduced colocalization of NM2A and F-actin in cells. Knockdown of ASAP1 or NM2A recapitulated each other's effects on FAs, cell migration, cell spreading, and CDRs. The NM2A-interacting BAR domain contributed to ASAP1 control of cell spreading and CDRs. Exogenous expression of NM2A rescued the effect of ASAP1 knockdown on CDRs but ASAP1 did not rescue NM2A knockdown defect in CDRs. Our results support the hypothesis that ASAP1 is a positive regulator of NM2A. Given other binding partners of ASAP1, ASAP1 may directly link signaling and the mechanical machinery of cell migration.
Collapse
Affiliation(s)
- Pei-Wen Chen
- From the Laboratory of Cellular and Molecular Biology and
| | - Xiaoying Jian
- From the Laboratory of Cellular and Molecular Biology and
| | | | - Kang Le
- Cardiovascular and Pulmonary Branch, NHLBI, National Institutes of Health, Bethesda, Maryland 20892
| | - Ruibai Luo
- From the Laboratory of Cellular and Molecular Biology and
| | | | | | - Joel Moss
- Cardiovascular and Pulmonary Branch, NHLBI, National Institutes of Health, Bethesda, Maryland 20892
| | | | | |
Collapse
|
22
|
Jian X, Tang WK, Zhai P, Roy NS, Luo R, Gruschus JM, Yohe ME, Chen PW, Li Y, Byrd RA, Xia D, Randazzo PA. Molecular Basis for Cooperative Binding of Anionic Phospholipids to the PH Domain of the Arf GAP ASAP1. Structure 2015; 23:1977-88. [PMID: 26365802 PMCID: PMC4788500 DOI: 10.1016/j.str.2015.08.008] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2015] [Revised: 08/12/2015] [Accepted: 08/14/2015] [Indexed: 11/18/2022]
Abstract
We have defined the molecular basis for association of the PH domain of the Arf GAP ASAP1 with phospholipid bilayers. Structures of the unliganded and dibutyryl PtdIns(4,5)P2-bound PH domain were solved. PtdIns(4,5)P2 made contact with both a canonical site (C site) and an atypical site (A site). We hypothesized cooperative binding of PtdIns(4,5)P2 to the C site and a nonspecific anionic phospholipid to the A site. PtdIns(4,5)P2 dependence of binding to large unilamellar vesicles and GAP activity was sigmoidal, consistent with cooperative sites. In contrast, PtdIns(4,5)P2 binding to the PH domain of PLC δ1 was hyperbolic. Mutation of amino acids in either the C or A site resulted in decreased PtdIns(4,5)P2-dependent binding to vesicles and decreased GAP activity. The results support the idea of cooperative phospholipid binding to the C and A sites of the PH domain of ASAP1. We propose that the mechanism underlies rapid switching between active and inactive ASAP1.
Collapse
Affiliation(s)
- Xiaoying Jian
- Laboratory of Cellular and Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Wai-Kwan Tang
- Laboratory of Cell Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Peng Zhai
- Laboratory of Cellular and Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Neeladri Sekhar Roy
- Laboratory of Cellular and Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Ruibai Luo
- Laboratory of Cellular and Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - James M Gruschus
- Laboratory of Structural Biophysics, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Marielle E Yohe
- Genetics Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Pei-Wen Chen
- Laboratory of Cellular and Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Yifei Li
- Structural Biophysics Laboratory, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - R Andrew Byrd
- Structural Biophysics Laboratory, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Di Xia
- Laboratory of Cell Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA; Laboratory of Cell Biology, National Cancer Institute, Building 37, Room 2122, Bethesda, MD 20892, USA.
| | - Paul A Randazzo
- Laboratory of Cellular and Molecular Biology, National Cancer Institute, National Institutes of Health, Building 37, Room 2042, Bethesda, MD 20892, USA.
| |
Collapse
|
23
|
Abstract
Mammalian cells have many membranous organelles that require proper composition of proteins and lipids. Cargo sorting is a process required for transporting specific proteins and lipids to appropriate organelles, and if this process is disrupted, organelle function as well as cell function is disrupted. ArfGAP family proteins have been found to be critical for receptor sorting. In this review, we summarize our recent knowledge about the mechanism of cargo sorting that require function of ArfGAPs in promoting the formation of transport vesicles, and discuss the involvement of specific ArfGAPs for the sorting of a variety of receptors, such as MPR, EGFR, TfR, Glut4, TRAIL-R1/DR4, M5-muscarinic receptor, c-KIT, rhodopsin and β1-integrin. Given the importance of many of these receptors to human disease, the studies of ArfGAPs may provide novel therapeutic strategies in addition to providing mechanistic insight of receptor sorting.
Collapse
Affiliation(s)
- Yoko Shiba
- Laboratory of Cellular and Molecular Biology, National Cancer Institute, Bethesda, MD20892, USA
| | - Paul A Randazzo
- Laboratory of Cellular and Molecular Biology, National Cancer Institute, Bethesda, MD20892, USA
| |
Collapse
|
24
|
Miyazaki M, Nishihara H, Hasegawa H, Tashiro M, Wang L, Kimura T, Tanino M, Tsuda M, Tanaka S. NS1-binding protein abrogates the elevation of cell viability by the influenza A virus NS1 protein in association with CRKL. Biochem Biophys Res Commun 2013; 441:953-7. [PMID: 24220336 DOI: 10.1016/j.bbrc.2013.11.011] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2013] [Accepted: 11/01/2013] [Indexed: 10/26/2022]
Abstract
The influenza A virus non-structural protein 1 (NS1) is a multifunctional virulence factor consisting of an RNA binding domain and several Src-homology (SH) 2 and SH3 binding motifs, which promotes virus replication in the host cell and helps to evade antiviral immunity. NS1 modulates general host cell physiology in association with various cellular molecules including NS1-binding protein (NS1-BP) and signaling adapter protein CRK-like (CRKL), while the physiological role of NS1-BP during influenza A virus infection especially in association with NS1 remains unclear. In this study, we analyzed the intracellular association of NS1-BP, NS1 and CRKL to elucidate the physiological roles of these molecules in the host cell. In HEK293T cells, enforced expression of NS1 of A/Beijing (H1N1) and A/Indonesia (H5N1) significantly induced excessive phosphorylation of ERK and elevated cell viability, while the over-expression of NS1-BP and the abrogation of CRKL using siRNA abolished such survival effect of NS1. The pull-down assay using GST-fusion CRKL revealed the formation of intracellular complexes of NS1-BP, NS1 and CRKL. In addition, we identified that the N-terminus SH3 domain of CRKL was essential for binding to NS1-BP using GST-fusion CRKL-truncate mutants. This is the first report to elucidate the novel function of NS1-BP collaborating with viral protein NS1 in modulation of host cell physiology. In addition, an alternative role of adaptor protein CRKL in association with NS1 and NS1-BP during influenza A virus infection is demonstrated.
Collapse
Affiliation(s)
- Masaya Miyazaki
- Department of Cancer Pathology, Hokkaido University Graduate School of Medicine, N15W7, Kita-ku, Sapporo 060-8638, Japan
| | | | | | | | | | | | | | | | | |
Collapse
|
25
|
The BAR Domain Superfamily Proteins from Subcellular Structures to Human Diseases. MEMBRANES 2012; 2:91-117. [PMID: 24957964 PMCID: PMC4021885 DOI: 10.3390/membranes2010091] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/05/2012] [Revised: 02/07/2012] [Accepted: 02/15/2012] [Indexed: 12/11/2022]
Abstract
Eukaryotic cells have complicated membrane systems. The outermost plasma membrane contains various substructures, such as invaginations and protrusions, which are involved in endocytosis and cell migration. Moreover, the intracellular membrane compartments, such as autophagosomes and endosomes, are essential for cellular viability. The Bin-Amphiphysin-Rvs167 (BAR) domain superfamily proteins are important players in membrane remodeling through their structurally determined membrane binding surfaces. A variety of BAR domain superfamily proteins exist, and each family member appears to be involved in the formation of certain subcellular structures or intracellular membrane compartments. Most of the BAR domain superfamily proteins contain SH3 domains, which bind to the membrane scission molecule, dynamin, as well as the actin regulatory WASP/WAVE proteins and several signal transduction molecules, providing possible links between the membrane and the cytoskeleton or other machineries. In this review, we summarize the current information about each BAR superfamily protein with an SH3 domain(s). The involvement of BAR domain superfamily proteins in various diseases is also discussed.
Collapse
|
26
|
Mucha E, Fricke I, Schaefer A, Wittinghofer A, Berken A. Rho proteins of plants – Functional cycle and regulation of cytoskeletal dynamics. Eur J Cell Biol 2011; 90:934-43. [PMID: 21277045 DOI: 10.1016/j.ejcb.2010.11.009] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2010] [Revised: 11/25/2010] [Accepted: 11/25/2010] [Indexed: 10/24/2022] Open
|
27
|
The non-catalytic carboxyl-terminal domain of ARFGAP1 regulates actin cytoskeleton reorganization by antagonizing the activation of Rac1. PLoS One 2011; 6:e18458. [PMID: 21483700 PMCID: PMC3070737 DOI: 10.1371/journal.pone.0018458] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2010] [Accepted: 03/08/2011] [Indexed: 11/26/2022] Open
Abstract
Background The regulation of the actin cytoskeleton and membrane trafficking is coordinated in mammalian cells. One of the regulators of membrane traffic, the small GTP-binding protein ARF1, also activates phosphatidylinositol kinases that in turn affect actin polymerization. ARFGAP1 is a GTPase activating protein (GAP) for ARF1 that is found on Golgi membranes. We present evidence that ARFGAP1 not only serves as a GAP for ARF1, but also can affect the actin cytoskeleton. Principal Findings As cells attach to a culture dish foci of actin appear prior to the cells flattening and spreading. We have observed that overexpression of a truncated ARFGAP1 that lacks catalytic activity for ARF, called GAP273, caused these foci to persist for much longer periods than non-transfected cells. This phenomenon was dependent on the level of GAP273 expression. Furthermore, cell spreading after re-plating or cell migration into a previously scraped area was inhibited in cells transfected with GAP273. Live cell imaging of such cells revealed that actin-rich membrane blebs formed that seldom made protrusions of actin spikes or membrane ruffles, suggesting that GAP273 interfered with the regulation of actin dynamics during cell spreading. The over-expression of constitutively active alleles of ARF6 and Rac1 suppressed the effect of GAP273 on actin. In addition, the activation of Rac1 by serum, but not that of RhoA or ARF6, was inhibited in cells over-expressing GAP273, suggesting that Rac1 is a likely downstream effector of ARFGAP1. The carboxyl terminal 65 residues of ARFGAP1 were sufficient to produce the effects on actin and cell spreading in transfected cells and co-localized with cortical actin foci. Conclusions ARFGAP1 functions as an inhibitor upstream of Rac1 in regulating actin cytoskeleton. In addition to its GAP catalytic domain and Golgi binding domain, it also has an actin regulation domain in the carboxyl-terminal portion of the protein.
Collapse
|
28
|
ASAP1 promotes tumor cell motility and invasiveness, stimulates metastasis formation in vivo, and correlates with poor survival in colorectal cancer patients. Oncogene 2010; 29:2393-403. [PMID: 20154719 DOI: 10.1038/onc.2010.6] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
We have previously performed an unbiased screen to identify genes whose expression is associated with the metastatic phenotype. Secondary screening of these genes using custom microarray chips identified ASAP1, a multi-domain adaptor protein with ADP-ribosylation factor-GAP activity, as being potentially involved in tumor progression. Here, we show that at least three different splice forms of ASAP1 are upregulated in rodent tumor models in a manner that correlates with metastatic potential. In human cancers, we found that ASAP1 expression is strongly upregulated in a variety of tumors in comparison with normal tissue and that this expression correlates with poor metastasis-free survival and prognosis in colorectal cancer patients. Using loss and gain of function approaches, we were able to show that ASAP1 promotes metastasis formation in vivo and stimulates tumor cell motility, invasiveness, and adhesiveness in vitro. Furthermore, we show that ASAP1 interacts with the metastasis-promoting protein h-prune and stimulates its phosphodiesterase activity. In addition, ASAP1 binds to the SH3 domains of several proteins, including SLK with which it co-immunoprecipitates. These data support the notion that ASAP1 can contribute to the dissemination of a variety of tumor types and represent a potential target for cancer therapy.
Collapse
|
29
|
Campa F, Yoon HY, Ha VL, Szentpetery Z, Balla T, Randazzo PA. A PH domain in the Arf GTPase-activating protein (GAP) ARAP1 binds phosphatidylinositol 3,4,5-trisphosphate and regulates Arf GAP activity independently of recruitment to the plasma membranes. J Biol Chem 2009; 284:28069-28083. [PMID: 19666464 DOI: 10.1074/jbc.m109.028266] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
ARAP1 is a phosphatidylinositol 3,4,5-trisphosphate (PtdIns(3,4,5)P(3))-dependent Arf GTPase-activating protein (GAP) with five PH domains that regulates endocytic trafficking of the epidermal growth factor receptor (EGFR). Two tandem PH domains are immediately N-terminal of the Arf GAP domain, and one of these fits the consensus sequence for PtdIns(3,4,5)P(3) binding. Here, we tested the hypothesis that PtdIns(3,4,5)P(3)-dependent recruitment mediated by the first PH domain of ARAP1 regulates the in vivo and in vitro function of ARAP1. We found that PH1 of ARAP1 specifically bound to PtdIns(3,4,5)P(3), but with relatively low affinity (approximately 1.6 microm), and the PH domains did not mediate PtdIns(3,4,5)P(3)-dependent recruitment to membranes in cells. However, PtdIns(3,4,5)P(3) binding to the PH domain stimulated GAP activity and was required for in vivo function of ARAP1 as a regulator of endocytic trafficking of the EGFR. Based on these results, we propose a variation on the model for the function of phosphoinositide-binding PH domains. In our model, ARAP1 is recruited to membranes independently of PtdIns(3,4,5)P(3), the subsequent production of which triggers enzymatic activity.
Collapse
Affiliation(s)
- Fanny Campa
- Laboratory of Cellular and Molecular Biology, NCI, National Institutes of Health, Bethesda, Maryland 20892
| | - Hye-Young Yoon
- Laboratory of Cellular and Molecular Biology, NCI, National Institutes of Health, Bethesda, Maryland 20892
| | - Vi Luan Ha
- Laboratory of Cellular and Molecular Biology, NCI, National Institutes of Health, Bethesda, Maryland 20892
| | - Zsofia Szentpetery
- Program for Developmental Neuroscience, NICHD, National Institutes of Health, Bethesda, Maryland 20892
| | - Tamas Balla
- Program for Developmental Neuroscience, NICHD, National Institutes of Health, Bethesda, Maryland 20892
| | - Paul A Randazzo
- Laboratory of Cellular and Molecular Biology, NCI, National Institutes of Health, Bethesda, Maryland 20892.
| |
Collapse
|
30
|
Campa F, Randazzo PA. Arf GTPase-activating proteins and their potential role in cell migration and invasion. Cell Adh Migr 2008; 2:258-62. [PMID: 19262159 DOI: 10.4161/cam.2.4.6959] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Cell migration is central to normal physiology in embryogenesis, the inflammatory response and wound healing. In addition, the acquisition of a motile and invasive phenotype is an important step in the development of tumors and metastasis. Arf GTPase-activating proteins (GAPs) are nonredundant regulators of specialized membrane surfaces implicated in cell migration. Part of Arf GAP function is mediated by regulating the ADP ribosylation factor (Arf) family GTP-binding proteins. However, Arf GAPs can also function independently of their GAP enzymatic activity, in some cases working as Arf effectors. In this commentary, we discuss examples of Arf GAPs that function either as regulators of Arfs or independently of the GTPase activity to regulate membrane structures that mediate cell adhesion and movement.
Collapse
Affiliation(s)
- Fanny Campa
- Laboratory of Cellular and Molecular Biology, National Cancer Institute, Bethesda, Maryland 20892-4256, USA
| | | |
Collapse
|
31
|
Inoue H, Ha VL, Prekeris R, Randazzo PA. Arf GTPase-activating protein ASAP1 interacts with Rab11 effector FIP3 and regulates pericentrosomal localization of transferrin receptor-positive recycling endosome. Mol Biol Cell 2008; 19:4224-37. [PMID: 18685082 DOI: 10.1091/mbc.e08-03-0290] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
ADP-ribosylation factors (Arfs) and Arf GTPase-activating proteins (GAPs) are key regulators of membrane trafficking and the actin cytoskeleton. The Arf GAP ASAP1 contains an N-terminal BAR domain, which can induce membrane tubulation. Here, we report that the BAR domain of ASAP1 can also function as a protein binding site. Two-hybrid screening identified FIP3, which is a putative Arf6- and Rab11-effector, as a candidate ASAP1 BAR domain-binding protein. Both coimmunoprecipitation and in vitro pulldown assays confirmed that ASAP1 directly binds to FIP3 through its BAR domain. ASAP1 formed a ternary complex with Rab11 through FIP3. FIP3 binding to the BAR domain stimulated ASAP1 GAP activity against Arf1, but not Arf6. ASAP1 colocalized with FIP3 in the pericentrosomal endocytic recycling compartment. Depletion of ASAP1 or FIP3 by small interfering RNA changed the localization of transferrin receptor, which is a marker of the recycling endosome, in HeLa cells. The depletion also altered the trafficking of endocytosed transferrin. These results support the conclusion that ASAP1, like FIP3, functions as a component of the endocytic recycling compartment.
Collapse
Affiliation(s)
- Hiroki Inoue
- Laboratory of Cellular and Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | | | | | | |
Collapse
|
32
|
Ha VL, Bharti S, Inoue H, Vass WC, Campa F, Nie Z, de Gramont A, Ward Y, Randazzo PA. ASAP3 is a focal adhesion-associated Arf GAP that functions in cell migration and invasion. J Biol Chem 2008; 283:14915-26. [PMID: 18400762 DOI: 10.1074/jbc.m709717200] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
ASAP3, an Arf GTPase-activating protein previously called DDEFL1 and ACAP4, has been implicated in the pathogenesis of hepatocellular carcinoma. We have examined in vitro and in vivo functions of ASAP3 and compared it to the related Arf GAP ASAP1 that has also been implicated in oncogenesis. ASAP3 was biochemically similar to ASAP1: the pleckstrin homology domain affected function of the catalytic domain by more than 100-fold; catalysis was stimulated by phosphatidylinositol 4,5-bisphosphate; and Arf1, Arf5, and Arf6 were used as substrates in vitro. Like ASAP1, ASAP3 associated with focal adhesions and circular dorsal ruffles. Different than ASAP1, ASAP3 did not localize to invadopodia or podosomes. Cells, derived from a mammary carcinoma and from a glioblastoma, with reduced ASAP3 expression had fewer actin stress fiber, reduced levels of phosphomyosin, and migrated more slowly than control cells. Reducing ASAP3 expression also slowed invasion of mammary carcinoma cells. In contrast, reduction of ASAP1 expression had no effect on migration or invasion. We propose that ASAP3 functions nonredundantly with ASAP1 to control cell movement and may have a role in cancer cell invasion. In comparing ASAP1 and ASAP3, we also found that invadopodia are dispensable for the invasive behavior of cells derived from a mammary carcinoma.
Collapse
Affiliation(s)
- Vi Luan Ha
- Laboratory of Cellular and Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | | | | | | | | | | | | | | | | |
Collapse
|
33
|
Abstract
The Arf (ADP-ribosylation factor) GAPs (GTPase-activating proteins) are a family of proteins with a common catalytic domain that induces hydrolysis of GTP bound to Arf GTP-binding proteins. At least three groups of multidomain Arf GAPs affect the actin cytoskeleton and cellular activities, such as migration and movement, that depend on the cytoskeleton. One role of the Arf GAPs is to regulate membrane remodelling that accompanies actin polymerization. Regulation of membrane remodelling is mediated in part by the regulation of Arf proteins. However, Arf GAPs also regulate actin independently of effects on membranes or Arf. These functions include acting as upstream regulators of Rho family proteins and providing a scaffold for Rho effectors and exchange factors. With multiple functional elements, the Arf GAPs could integrate signals and biochemical activities that result in co-ordinated changes in actin and membranes necessary for a wide range of cellular functions.
Collapse
Affiliation(s)
- Paul A Randazzo
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, MD 20892, USA.
| | | | | |
Collapse
|
34
|
Ha VL, Luo R, Nie Z, Randazzo PA. Contribution of AZAP-Type Arf GAPs to cancer cell migration and invasion. Adv Cancer Res 2008; 101:1-28. [PMID: 19055940 PMCID: PMC7249260 DOI: 10.1016/s0065-230x(08)00401-6] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Arf GAPs are a family of proteins with a common catalytic domain that induces hydrolysis of GTP bound to the small GTP-binding protein Arf. The proteins are otherwise structurally diverse. Several subtypes of Arf GAPs have been found to be targets of oncogenes and to control cell proliferation and cell migration. The latter effects are thought to be mediated by coordinating changes in actin remodeling and membrane traffic. In this chapter, we discuss Arf GAPs that have been linked to oncogenesis and the molecular mechanisms underlying the effects of these proteins in cancer cells. We also discuss the enzymology of the Arf GAPs related to possible targeted inhibition of specific subtypes of Arf GAPs.
Collapse
Affiliation(s)
- Vi Luan Ha
- Laboratory of Cellular and Molecular Biology, National Cancer Institute, Bethesda, Maryland, USA
| | | | | | | |
Collapse
|
35
|
Bharti S, Inoue H, Bharti K, Hirsch DS, Nie Z, Yoon HY, Artym V, Yamada KM, Mueller SC, Barr VA, Randazzo PA. Src-dependent phosphorylation of ASAP1 regulates podosomes. Mol Cell Biol 2007; 27:8271-83. [PMID: 17893324 PMCID: PMC2169185 DOI: 10.1128/mcb.01781-06] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Invadopodia are Src-induced cellular structures that are thought to mediate tumor invasion. ASAP1, an Arf GTPase-activating protein (GAP) containing Src homology 3 (SH3) and Bin, amphiphysin, and RVS161/167 (BAR) domains, is a substrate of Src that controls invadopodia. We have examined the structural requirements for ASAP1-dependent formation of invadopodia and related structures in NIH 3T3 fibroblasts called podosomes. We found that both predominant splice variants of ASAP1 (ASAP1a and ASAP1b) associated with invadopodia and podosomes. Podosomes were highly dynamic, with rapid turnover of both ASAP1 and actin. Reduction of ASAP1 levels by small interfering RNA blocked formation of invadopodia and podosomes. Podosomes were formed in NIH 3T3 fibroblasts in which endogenous ASAP1 was replaced with either recombinant ASAP1a or ASAP1b. ASAP1 mutants that lacked the Src binding site or GAP activity functioned as well as wild-type ASAP1 in the formation of podosomes. Recombinant ASAP1 lacking the BAR domain, the SH3 domain, or the Src phosphorylation site did not support podosome formation. Based on these results, we conclude that ASAP1 is a critical target of tyrosine kinase signaling involved in the regulation of podosomes and invadopodia and speculate that ASAP1 may function as a coincidence detector of simultaneous protein association through the ASAP1 SH3 domain and phosphorylation by Src.
Collapse
Affiliation(s)
- Sanita Bharti
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, MD 20892, USA
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
36
|
Abstract
Membrane trafficking and remodeling of the actin cytoskeleton are critical activities contributing to cellular events that include cell growth, migration and tumor invasion. ADP-ribosylation factor (Arf)-directed GTPase activating proteins (GAPs) have crucial roles in these processes. The Arf GAPs function in part by regulating hydrolysis of GTP bound to Arf proteins. The Arf GAPs, which have multiple functional domains, also affect the actin cytoskeleton and membranes by specific interactions with lipids and proteins. A description of these interactions provides insights into the molecular mechanisms by which Arf GAPs regulate physiological and pathological cellular events. Here we describe the Arf GAP family and summarize the currently identified protein interactors in the context of known Arf GAP functions.
Collapse
Affiliation(s)
- Hiroki Inoue
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, MD 20892, USA
| | | |
Collapse
|
37
|
Yoon HY, Miura K, Cuthbert EJ, Davis KK, Ahvazi B, Casanova JE, Randazzo PA. ARAP2 effects on the actin cytoskeleton are dependent on Arf6-specific GTPase-activating-protein activity and binding to RhoA-GTP. J Cell Sci 2006; 119:4650-66. [PMID: 17077126 DOI: 10.1242/jcs.03237] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
ARAP2 is a protein that contains both ArfGAP and RhoGAP domains. We found that it is a phosphatidylinositol (3,4,5)-trisphosphate-dependent Arf6 GAP that binds RhoA-GTP but lacks RhoGAP activity. In agreement with the hypothesis that ARAP2 mediates effects of RhoA, endogenous ARAP2 associated with focal adhesions (FAs) and reduction of ARAP2 expression, by RNAi, resulted in fewer FAs and actin stress fibers (SFs). In cells with reduced levels of endogenous ARAP2, FAs and SFs could be restored with wild-type recombinant ARAP2 but not mutants lacking ArfGAP or Rho-binding activity. Constitutively active Arf6 also caused a loss of SFs. The Rho effector ROKα was ineffective in restoring FAs. Conversely, overexpression of ARAP2 did not restore SFs in cells treated with a ROK inhibitor but induced punctate accumulations of paxillin. We conclude that ARAP2 is an Arf6GAP that functions downstream of RhoA to regulate focal adhesion dynamics.
Collapse
Affiliation(s)
- Hye-Young Yoon
- Laboratory of Cellular Oncology, Center for Cancer Research, National Cancer Institute, Department of Health and Human Services, Building 37, Bethesda, MD 20892, USA
| | | | | | | | | | | | | |
Collapse
|
38
|
Choi W, Karim ZA, Whiteheart SW. Arf6 plays an early role in platelet activation by collagen and convulxin. Blood 2005; 107:3145-52. [PMID: 16352809 PMCID: PMC1895749 DOI: 10.1182/blood-2005-09-3563] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Small GTPases play critical roles in hemostasis, though the roster of such molecules in platelets is not complete. In this study, we report the presence of Ras-related GTPases of the ADP-ribosylation factor (Arf) family. Platelets contain Arf1 or 3 and Arf6, with the latter being predominantly membrane associated. Using effector domain pull-down assays, we show, counter to other GTPases, that Arf6-GTP is present in resting platelets and decreases rapidly upon activation with collagen or convulxin. This decrease does not completely rely on secondary agonists (ADP and thromboxane A2) or require integrin signaling. The decrease in free Arf6-GTP temporally precedes activation of Rho family GTPases (RhoA, Cdc42, and Rac1). Using a membrane-permeant, myristoylated peptide, which mimics the N-terminus of Arf6, we show that the Arf6-GTP decrease is essential for collagen- and convulxin-induced aggregation, platelet adherence, and spreading on collagen-coated glass. Treatment with this peptide also affects the activation of Rho family GTPases, but has little effect on RalA and Rap1 or on agonist-induced calcium mobilization. These data show that Arf6 is a key element in activation through GPVI, and is required for activation of the Rho family GTPases and the subsequent cytoskeletal rearrangements needed for full platelet function.
Collapse
Affiliation(s)
- Wangsun Choi
- Department of Molecular and Cellular Biochemistry, University of Kentucky College of Medicine, Lexington, KY 40536-0509, USA
| | | | | |
Collapse
|
39
|
Abstract
Centaurin beta4 proteins are products of the DDEF1 (development and differentiation-enhancing factor 1) locus on human chromosome 8q24.1-24.2. Recent reports have indicated that this region and its products are amplified during development of several human cancers. Centaurins are GAPs (GTPase-activating proteins) that, together with GEFs (guanine nucleotide-exchange factors), regulate cyclic activation of Arfs (ADP-ribosylation factors), members of the Ras GTPase superfamily. Centaurin beta4 proteins associate with a variety of cellular signalling components implicated in control of growth, survival and movement and may act to direct assembly and/or disassembly of molecular complexes in concert with Arf, lipid and protein phosphorylation signalling pathways.
Collapse
|
40
|
Che MM, Boja ES, Yoon HY, Gruschus J, Jaffe H, Stauffer S, Schuck P, Fales HM, Randazzo PA. Regulation of ASAP1 by phospholipids is dependent on the interface between the PH and Arf GAP domains. Cell Signal 2005; 17:1276-88. [PMID: 16038802 DOI: 10.1016/j.cellsig.2005.01.007] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2004] [Revised: 01/16/2005] [Accepted: 01/19/2005] [Indexed: 10/25/2022]
Abstract
ASAP1 is an Arf GAP with a PH domain immediately N-terminal to the catalytic Arf GAP domain. PH domains are thought to regulate enzymes by binding to specific phosphoinositide lipids in membranes, thereby recruiting the enzyme to a site of action. Here, we have examined the functional relationship between the PH and Arf GAP domains. We found that GAP activity requires the cognate PH domain of ASAP1, leading us to hypothesize that the Arf GAP and PH domains directly interact to form the substrate binding site. This hypothesis was supported by the combined results of protection and hydrodynamic studies. We then examined the role of the PH domain in the regulation of Arf GAP activity. The results of saturation kinetics, limited proteolysis, FRET and fluorescence spectrometry support a model in which regulation of the GAP activity of ASAP1 involves a conformational change coincident with recruitment to a membrane surface, and a second conformational change following the specific binding of phosphatidylinositol 4,5-bisphosphate.
Collapse
Affiliation(s)
- Magnus M Che
- Laboratory of Cellular Oncology, Center for Cancer Research, National Cancer Institute, United States
| | | | | | | | | | | | | | | | | |
Collapse
|
41
|
Okuda K, Oda A, Sato Y, Nakayama A, Fujita H, Sonoda Y, Griffin JD. Signal transduction and cellular functions of the TEL/ARG oncoprotein. Leukemia 2005; 19:603-10. [PMID: 15729383 DOI: 10.1038/sj.leu.2403668] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The TEL/ARG oncogene is formed by t(1;12)(q25;p13) reciprocal translocation and is associated with human leukemia. We have previously demonstrated that the expression of TEL/ARG in Ba/F3 cells results in prolonged viability and hyper-responsiveness to IL-3. To determine the molecular mechanisms, a series of mutants of TEL/ARG were generated, and each cDNA was expressed in Ba/F3 or CHO cells. The PNT domain in TEL and K317 in ARG were essential for both signaling and biological effects. The SH3 domain in ARG was required for hyper-responsiveness to IL-3, but not for prolonged viability. The opposite was true for the SH2 domain in ARG. Mutation of Y314 in TEL, a putative GRB2-binding site, led to reduced viability, and loss of hyper-responsiveness to IL-3. All biological functions were profoundly impaired with deletion of the C-terminus in ARG, despite maintaining high levels of its kinase activity. When expressed in CHO cells, wild-type TEL/ARG induced the formation of fillopodia, in a fashion dependent on the C-terminal portion and intact kinase activity. Thus, these results suggest several critical domains within TEL/ARG necessary for function, and indicate that the signaling pathways necessary for viability, growth factor hyper-responsiveness and cytoskeletal reorganization are likely to be separate.
Collapse
Affiliation(s)
- K Okuda
- Department of Health Sciences and Preventive Medicine, Kyoto Prefectural University of Medicine, Kyoto, Japan.
| | | | | | | | | | | | | |
Collapse
|
42
|
Zhuang X, Xu Y, Chong K, Lan L, Xue Y, Xu Z. OsAGAP, an ARF-GAP from rice, regulates root development mediated by auxin in Arabidopsis. PLANT, CELL & ENVIRONMENT 2005; 28:147-56. [PMID: 16010732 DOI: 10.1111/j.1365-3040.2004.01253.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Arf (ADP-ribosylation factor) proteins, which mediate vesicular transport, have little or no intrinsic GTPase activity. They rely on the action of GTPase-activating proteins (GAPs) and guanine nucleotide exchange factors (GEFs) for their function. In the present study the OsAGAP gene in rice, which encoded a protein with predicted structure similar to ArfGAP, was identified. The purified OsAGAP-GST fusion protein was able to stimulate the GTPase activity of rice Arf. Furthermore, OsAGAP can rescue the defect of vesicular transport in the yeast gcs1 delta glo3 delta double-mutant cells. Transgenic Arabidopsis with OsAGAP constitutively expression showed reduced apical dominance, shorter primary roots, increasing number of longer adventitious roots. Many of the phenotypes can be phenocopied by treatment of exogenous indoleacetic acid level (IAA) in wild-type plants. Determination of whole-plant IAA level showed that there is a sharp increase of free IAA in OsAGAP transgenic Arabidopsis seedlings. In addition, removal of the 4-day-old shoot apex could inhibit the adventitious root formation in the transgenic seedlings. These results suggest OsAGAP, an ARF-GAP of rice, maybe involved in the mediation of plant root development by regulating auxin level.
Collapse
Affiliation(s)
- X Zhuang
- Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, CAS, Beijing, China
| | | | | | | | | | | |
Collapse
|
43
|
Randazzo PA, Hirsch DS. Arf GAPs: multifunctional proteins that regulate membrane traffic and actin remodelling. Cell Signal 2004; 16:401-13. [PMID: 14709330 DOI: 10.1016/j.cellsig.2003.09.012] [Citation(s) in RCA: 137] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The ADP-ribosylation factor (Arf) Arf GTPase-activating proteins (GAPs) are a family of proteins that induce hydrolysis of GTP bound to Arf. A conserved domain containing a zinc finger motif mediates catalysis. The substrate, Arf.GTP, affects membrane trafficking and actin remodelling. Consistent with activity as an Arf regulator, the Arf GAPs affect both of these pathways. However, the Arf GAPs are likely to have Arf-independent activities that contribute to their cellular functions. Structures of the Arf GAPs are diverse containing catalytic, protein-protein interaction and lipid interaction domains in addition to the Arf GAP domain. Some Arf GAPs have been identified and characterized on the basis of activities other than Arf GAP. Here, we describe the Arf GAP family, enzymology of some members of the Arf GAP family and known functions of the proteins. The results discussed illustrate roles for both Arf-dependent and -independent activities in the regulation of cellular architecture.
Collapse
Affiliation(s)
- Paul A Randazzo
- Laboratory of Cellular Oncology, Center for Cancer Research, National Cancer Institute, Building. 37 Room 4118, Bethesda, MD 20892, USA.
| | | |
Collapse
|