1
|
Molecular Mechanisms Involved in Neural Substructure Development during Phosphodiesterase Inhibitor Treatment of Mesenchymal Stem Cells. Int J Mol Sci 2020; 21:ijms21144867. [PMID: 32660142 PMCID: PMC7402296 DOI: 10.3390/ijms21144867] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2020] [Revised: 07/03/2020] [Accepted: 07/06/2020] [Indexed: 12/14/2022] Open
Abstract
Stem cells are highly important in biology due to their unique innate ability to self-renew and differentiate into other specialised cells. In a neurological context, treating major injuries such as traumatic brain injury, spinal cord injury and stroke is a strong basis for research in this area. Mesenchymal stem cells (MSC) are a strong candidate because of their accessibility, compatibility if autologous, high yield and multipotency with a potential to generate neural cells. With the use of small-molecule chemicals, the neural induction of stem cells may occur within minutes or hours. Isobutylmethyl xanthine (IBMX) has been widely used in cocktails to induce neural differentiation. However, the key molecular mechanisms it instigates in the process are largely unknown. In this study we showed that IBMX-treated mesenchymal stem cells induced differentiation within 24 h with the unique expression of several key proteins such as Adapter protein crk, hypoxanthine-guanine phosphoribosyltransferase, DNA topoisomerase 2-beta and Cell division protein kinase 5 (CDK5), vital in linking signalling pathways. Furthermore, the increased expression of basic fibroblast growth factor in treated cells promotes phosphatidylinositol 3-kinase (PI3K), mitogen-activated protein kinase (MAPK) cascades and GTPase–Hras interactions. Bioinformatic and pathway analyses revealed upregulation in expression and an increase in the number of proteins with biological ontologies related to neural development and substructure formation. These findings enhance the understanding of the utility of IBMX in MSC neural differentiation and its involvement in neurite substructure development.
Collapse
|
2
|
Crk adaptor proteins regulate CD3ζ chain phosphorylation and TCR/CD3 down-modulation in activated T cells. Cell Signal 2017; 36:117-126. [PMID: 28465009 DOI: 10.1016/j.cellsig.2017.04.022] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2017] [Revised: 04/15/2017] [Accepted: 04/26/2017] [Indexed: 01/06/2023]
Abstract
T cell receptor (TCR) recognition of a peptide antigen in the context of MHC molecules initiates positive and negative cascades that regulate T cell activation, proliferation and differentiation, and culminate in the acquisition of effector T cell functions. These processes are a prerequisite for the induction of specific T cell-mediated adaptive immune responses. A key event in the activation of TCR-coupled signaling pathways is the phosphorylation of tyrosine residues within the cytoplasmic tails of the CD3 subunits, predominantly CD3ζ. These transiently formed phosphotyrosyl epitopes serve as docking sites for SH2-domain containing effector molecules, predominantly the ZAP70 protein tyrosine kinase, which is critical for signal propagation. We found that CrkI and CrkII adaptor proteins also interact with CD3ζ in TCR activated-, but not in resting-, T cells. Crk binding to CD3ζ was independent of ZAP70 and also occurred in ZAP70-deficient T cells. Binding was mediated by Crk-SH2 domain interaction with phosphotyrosine-containing motifs on CD3ζ, via a direct physical interaction, as demonstrated by Far-Western blot. CrkII binding to CD3ζ could also be demonstrated in a heterologous system, where coexpression of a catalytically active Lck was used to phosphorylate the CD3ζ chain. TCR activation-induced Crk binding to CD3ζ resulted in increased and prolonged phosphorylation of CD3ζ, as well as ZAP70 and LAT, suggesting a positive role for CrkI/II binding to CD3ζ in regulation of TCR-coupled signaling pathways. Furthermore, Crk-dependent increased phosphorylation of CD3ζ coincided with inhibition of TCR downmodulation, supporting a positive role for Crk adaptor proteins in TCR-mediated signal amplification.
Collapse
|
3
|
Garrett CA, Barri M, Kuta A, Soura V, Deng W, Fisher EMC, Schiavo G, Hafezparast M. DYNC1H1 mutation alters transport kinetics and ERK1/2-cFos signalling in a mouse model of distal spinal muscular atrophy. ACTA ACUST UNITED AC 2014; 137:1883-93. [PMID: 24755273 DOI: 10.1093/brain/awu097] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Mutations in the gene encoding the heavy chain subunit (DYNC1H1) of cytoplasmic dynein cause spinal muscular atrophy with lower extremity predominance, Charcot-Marie-Tooth disease and intellectual disability. We used the legs at odd angles (Loa) (DYNC1H1(F580Y)) mouse model for spinal muscular atrophy with lower extremity predominance and a combination of live-cell imaging and biochemical assays to show that the velocity of dynein-dependent microtubule minus-end (towards the nucleus) movement of EGF and BDNF induced signalling endosomes is significantly reduced in Loa embryonic fibroblasts and motor neurons. At the same time, the number of the plus-end (towards the cell periphery) moving endosomes is increased in the mutant cells. As a result, the extracellular signal-regulated kinases (ERK) 1/2 activation and c-Fos expression are altered in both mutant cell types, but the motor neurons exhibit a strikingly abnormal ERK1/2 and c-Fos response to serum-starvation induced stress. These data highlight the cell-type specific ERK1/2 response as a possible contributory factor in the neuropathological nature of Dync1h1 mutations, despite generic aberrant kinetics in both cell types, providing an explanation for how mutations in the ubiquitously expressed DYNC1H1 cause neuron-specific disease.
Collapse
Affiliation(s)
- Caroline A Garrett
- 1 School of Life Sciences, University of Sussex, Falmer, Brighton, BN1 9QG, UK
| | - Muruj Barri
- 1 School of Life Sciences, University of Sussex, Falmer, Brighton, BN1 9QG, UK
| | - Anna Kuta
- 2 Department of Neurodegenerative Disease, Institute of Neurology, University College London, Queen Square, London WC1N 3BG, UK
| | - Violetta Soura
- 1 School of Life Sciences, University of Sussex, Falmer, Brighton, BN1 9QG, UK
| | - Wenhan Deng
- 1 School of Life Sciences, University of Sussex, Falmer, Brighton, BN1 9QG, UK
| | - Elizabeth M C Fisher
- 2 Department of Neurodegenerative Disease, Institute of Neurology, University College London, Queen Square, London WC1N 3BG, UK
| | - Giampietro Schiavo
- 3 Sobell Department of Motor Neuroscience and Movement Disorders, Institute of Neurology, University College London, Queen Square, London WC1N 3BG, UK
| | - Majid Hafezparast
- 1 School of Life Sciences, University of Sussex, Falmer, Brighton, BN1 9QG, UK
| |
Collapse
|
4
|
Wang H, Linghu H, Wang J, Che YL, Xiang TX, Tang WX, Yao ZW. The role of Crk/Dock180/Rac1 pathway in the malignant behavior of human ovarian cancer cell SKOV3. Tumour Biol 2009; 31:59-67. [PMID: 20237902 DOI: 10.1007/s13277-009-0009-9] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2009] [Accepted: 11/04/2009] [Indexed: 11/25/2022] Open
Abstract
Small GTPases, particularly the Rho family, are key regulators of cell motility and migration. Dock180 was well known for the main target of signal adaptor protein Crk and acted as a guanine-nucleotide exchange factor for small GTPase Rac1. In the present study, Dock180 was found to combine primarily with CrkI other than CrkII, and its association with Elmo1 was also demonstrated in ovarian cancer cell SKOV3. To evaluate the role of Dock180 in human ovarian cancer cell, we performed RNAi-mediated knockdown of Dock180 in SKOV3 cells using small interfering RNA expression vector. In Dock180 knockdown cells, we found that Elmo1 expression and Rac1 activity were decreased simultaneously. By contrast, the expressions of both another Crk-combining molecule C3G and Rap1 activity were observed to increase obviously. Accordingly, all Dock180 knockdown cells present with evident change in cell morphology, reduced cell proliferation, and attenuated cell migration. Taken together, these results suggest that signal transfer of Crk/Dock180/Rac1 is implicated in actin cytoskeleton reorganization and thus in the cell proliferation, motility, invasion, and of human ovarian cancer cell line SKOV3.
Collapse
Affiliation(s)
- Hui Wang
- Department of Obstetrics and Gynecology, The First Affiliated Hospital, Chongqing Medical University, Chongqing, 400016, China
| | | | | | | | | | | | | |
Collapse
|
5
|
Watanabe T, Tsuda M, Makino Y, Konstantinou T, Nishihara H, Majima T, Minami A, Feller SM, Tanaka S. Crk adaptor protein-induced phosphorylation of Gab1 on tyrosine 307 via Src is important for organization of focal adhesions and enhanced cell migration. Cell Res 2009; 19:638-50. [PMID: 19350053 DOI: 10.1038/cr.2009.40] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Upon growth factor stimulation, the scaffold protein, Gab1, is tyrosine phosphorylated and subsequently the adaptor protein, Crk, transmits signals from Gab1. We have previously shown that Crk overexpression, which is detectable in various human cancers, induces tyrosine phosphorylation of Gab1 without extracellular stimuli. In the present study, the underlying mechanisms were further investigated. Mutational analyses of CrkII demonstrated that the SH2 domain, but not the SH3(N) or the regulatory Y221 residue of CrkII, is critical for the induction of Gab1-Y307 phosphorylation. SH2 mutation of CrkII also decreased the interaction with Gab1. In GST pull-down assay, Crk-SH2 bound to wild-type Gab1, whereas Crk-SH3(N) interacted with the Gab1 mutant, which lacks the clustered tyrosine region (residues 242-410). Tyrosine phosphorylation of Gab1 was induced by all Crk family proteins, but not other SH2-containing signalling adaptors. Src-family kinase inhibitor, PP2, abrogates Crk-induced tyrosine phosphorylations of Gab1. Y307 phosphorylation was undetectable in fibroblasts lacking Src, Yes, and Fyn, even upon overexpression of Crk, whereas cells lacking only Yes and Fyn still contained Gab1 with phosphorylated Y307. Furthermore, Crk induced the phosphorylation of Src-Y416; accordingly the interaction between Crk and Csk was increased. The Gab1-Y307F mutant failed to localize near the plasma membrane even upon HGF stimulation and decreased cell migration. Moreover, Gab1-Y307F disturbed the localization of Crk, FAK, and paxillin, which are the typical components of focal adhesions. Taken together, these results indicate that Crk facilitates tyrosine phosphorylation of Gab1-Y307 through Src, contributing to the organization of focal adhesions and enhanced cell migration, thereby possibly promoting human cancer development.
Collapse
Affiliation(s)
- Takuya Watanabe
- Laboratory of Molecular and Cellular Pathology, Hokkaido University Graduate School of Medicine, N15, W7, Kita-ku, Sapporo 060-8638, Japan
| | | | | | | | | | | | | | | | | |
Collapse
|
6
|
Kobashigawa Y, Sakai M, Naito M, Yokochi M, Kumeta H, Makino Y, Ogura K, Tanaka S, Inagaki F. [Structural basis for the transforming activity of human cancer-related signaling adaptor protein Crk]. Nat Struct Mol Biol 2008; 14:503-10. [PMID: 17515907 DOI: 10.1038/nsmb1241] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2006] [Accepted: 03/27/2007] [Indexed: 01/13/2023]
Abstract
CRKI (SH2-SH3) and CRKII (SH2-SH3-SH3) are splicing isoforms of the oncoprotein CRK that regulate transcription and cytoskeletal reorganization for cell growth and motility by linking tyrosine kinases to small G proteins. CRKI shows substantial transforming activity, whereas the activity of CRKII is low, and phosphorylated CRKII has no biological activity whatsoever. The molecular mechanisms underlying the distinct biological activities of the CRK proteins remain elusive. We determined the solution structures of CRKI, CRKII and phosphorylated CRKII by NMR and identified the molecular mechanism that gives rise to their activities. Results from mutational analysis using rodent 3Y1 fibroblasts were consistent with those from the structural studies. Together, these data suggest that the linker region modulates the binding of CRKII to its targets, thus regulating cell growth and motility.
Collapse
Affiliation(s)
- Yoshihiro Kobashigawa
- Department of Structural Biology, Graduate School of Pharmaceutical Sciences, Hokkaido University, Sapporo, Hokkaido 060-0810, Japan
| | | | | | | | | | | | | | | | | |
Collapse
|
7
|
Gelkop S, Gish GD, Babichev Y, Pawson T, Isakov N. T cell activation-induced CrkII binding to the Zap70 protein tyrosine kinase is mediated by Lck-dependent phosphorylation of Zap70 tyrosine 315. THE JOURNAL OF IMMUNOLOGY 2006; 175:8123-32. [PMID: 16339550 DOI: 10.4049/jimmunol.175.12.8123] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The Zap70 protein tyrosine kinase controls TCR-linked signal transduction pathways and is critical for T cell development and responsiveness. Following engagement of TCR, the Zap70 undergoes phosphorylation on multiple tyrosine residues that are implicated in the regulation of its catalytic activity and interaction with signaling effector molecules downstream of the TCR. We have shown previously that the CT10 regulator of kinase II (CrkII) adapter protein interacts with tyrosine-phosphorylated Zap70 in TCR-engaged T cells, and now extend these studies to show that Tyr315 in the Zap70 interdomain B region is the site of interaction with CrkII. A point mutation of Tyr315 (Y315F) eliminated the CrkII-Zap70 interaction capacity. Phosphorylation of Tyr315 and Zap70 association with CrkII were both dependent upon the Lck protein tyrosine kinase. Previous studies demonstrated the Tyr315 is the Vav-Src homology 2 (SH2) binding site, and that replacement of Tyr315 by Phe impaired the function of Zap70 in TCR signaling. However, fluorescence polarization-based binding studies revealed that the CrkII-SH2 and the Vav-SH2 bind a phosphorylated Tyr315-Zap70-derived peptide with affinities of a similar order of magnitude (Kd of 2.5 and 1.02 microM, respectively). The results suggest therefore that the biological functions attributed to the association of Zap70 with Vav following T cell activation may equally reflect the association of Zap70 with CrkII, and further support a regulatory role for CrkII in the TCR-linked signal transduction pathway.
Collapse
Affiliation(s)
- Sigal Gelkop
- Department of Microbiology and Immunology, Faculty of Health Sciences, and the Cancer Research Center, Ben Gurion University of the Negev, Beer Sheva, Israel
| | | | | | | | | |
Collapse
|
8
|
Makino Y, Tsuda M, Ichihara S, Watanabe T, Sakai M, Sawa H, Nagashima K, Hatakeyama S, Tanaka S. Elmo1 inhibits ubiquitylation of Dock180. J Cell Sci 2006; 119:923-32. [PMID: 16495483 DOI: 10.1242/jcs.02797] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Dock180, a member of the CDM family of proteins, plays roles in biological processes such as phagocytosis and motility through its association with the signalling adaptor protein Crk. Recently, the complex formation between Dock180 and Elmo1 was reported to function as a bipartite guanine nucleotide exchange factor for Rac. In this study, we demonstrated that the amount of Dock180 increased when Elmo1 was co-expressed. Dock180 was found to be ubiquitylated and Dock180 protein levels could be augmented by treatment with proteasome inhibitor. The ubiquitylation of Dock180 was enhanced by epidermal growth factor (EGF), Crk and adhesion-dependent signals. Furthermore, Elmo1 inhibited ubiquitylation of Dock180, resulting in the increase in Dock180 levels. The Elmo1 mutant Δ531, which encompasses amino acids required for Dock180 binding, preserved the inhibitory effects on ubiquitylation of Dock180. Upon EGF stimulation, both Dock180 and ubiquitin were demonstrated to translocate to the cell periphery by immunofluorescence, and we found ubiquitylation of Dock180 and its inhibition by Elmo1 to occur in cellular membrane fractions by in vivo ubiquitylation assay. These data suggest that Dock180 is ubiquitylated on the plasma membrane, and also that Elmo1 functions as an inhibitor of ubiquitylation of Dock180. Therefore, an ubiquitin-proteasome-dependent protein degradation mechanism might contribute to the local activation of Rac on the plasma membrane.
Collapse
Affiliation(s)
- Yoshinori Makino
- Laboratory of Molecular and Cellular Pathology, Hokkaido University Graduate School of Medicine, N15, W7, Sapporo 060-8638, Japan
| | | | | | | | | | | | | | | | | |
Collapse
|
9
|
Linghu H, Tsuda M, Makino Y, Sakai M, Watanabe T, Ichihara S, Sawa H, Nagashima K, Mochizuki N, Tanaka S. Involvement of adaptor protein Crk in malignant feature of human ovarian cancer cell line MCAS. Oncogene 2006; 25:3547-56. [PMID: 16491127 DOI: 10.1038/sj.onc.1209398] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Signaling adaptor protein Crk regulates cell motility and growth through its targets Dock180 and C3G, those are the guanine-nucleotide exchange factors (GEFs) for small GTPases Rac and Rap, respectively. Recently, overexpression of Crk has been reported in various human cancers. To define the role for Crk in human cancer cells, Crk expression was targeted in the human ovarian cancer cell line MCAS through RNA interference, resulting in the establishment of three Crk knockdown cell lines. These cell lines exhibited disorganized actin fibers, reduced number of focal adhesions, and abolishment of lamellipodia formation. Decreased Rac activity was demonstrated by pull-down assay and FRET-based time-lapse microscopy, in association with suppression of both motility and invasion by phagokinetic track assay and transwell assay in these cells. Furthermore, Crk knockdown cells exhibited slow growth rates in culture and suppressed anchorage-dependent growth in soft agar. Tumor forming potential in nude mice was attenuated, and intraperitoneal dissemination was not observed when Crk knockdown cells were injected into the peritoneal cavity. These results suggest that the Crk is a key component of focal adhesion and involved in cell growth, invasion, and dissemination of human ovarian cancer cell line MCAS.
Collapse
Affiliation(s)
- H Linghu
- Laboratory of Molecular and Cellular Pathology, Hokkaido University Graduate School of Medicine, Sapporo, Hokkaido, Japan
| | | | | | | | | | | | | | | | | | | |
Collapse
|
10
|
Sasaki T, Iwata S, Okano HJ, Urasaki Y, Hamada J, Tanaka H, Dang NH, Okano H, Morimoto C. Nedd9 protein, a Cas-L homologue, is upregulated after transient global ischemia in rats: possible involvement of Nedd9 in the differentiation of neurons after ischemia. Stroke 2005; 36:2457-62. [PMID: 16210561 DOI: 10.1161/01.str.0000185672.10390.30] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND AND PURPOSE Some proteins involved in self-repair after stroke in the adult brain are primarily expressed during embryonic development and strongly down-regulated during the early postnatal phase. Neuronal precursor cell-expressed, developmentally down-regulated gene (Nedd) 9 was recognized to be identical to Crk-associated substrate lymphocyte type (Cas-L), a docking protein that associates with a variety of signaling molecules, such as focal adhesion kinase (FAK), proline-rich tyrosine kinase 2 (Pyk2), and Crk. We investigated the involvement of these proteins in the pathophysiology of global cerebral ischemia. METHODS The mouse Cas-L/Nedd9 cDNAs were cloned. The expression and function of Cas-L/Nedd9 protein in the pathogenesis of global ischemia in rats was investigated by RT-PCR, Western blot analysis, and immunohistochemistry. The neurite outgrowth of the transfectants of Nedd9 deletion mutants in PC-12 cells was also assessed to clarify the function of the Nedd9 protein. RESULTS Nedd9 was a splicing variant of Cas-L and was selectively induced in neurons of the cerebral cortex and hippocampus 1 to 14 days after the ischemia. Induced Nedd9 protein was tyrosine phosphorylated and was bound to FAK in dendrite and soma of neurons after the ischemia. Finally, it was demonstrated that Nedd9 promoted neurite outgrowth of PC-12 cells. CONCLUSIONS Our study may support the potential of Nedd9 for participation in the differentiation of neurons after global ischemia in rats.
Collapse
MESH Headings
- Adaptor Proteins, Signal Transducing
- Alternative Splicing
- Amino Acid Sequence
- Animals
- Blotting, Western
- Cell Differentiation
- Cerebral Cortex/metabolism
- Cerebral Cortex/pathology
- Cloning, Molecular
- Cytoskeletal Proteins/biosynthesis
- DNA, Complementary/metabolism
- Dendrites/pathology
- Down-Regulation
- Focal Adhesion Kinase 2/metabolism
- Focal Adhesion Protein-Tyrosine Kinases/metabolism
- Gene Deletion
- Gene Expression Regulation, Developmental
- Gene Transfer Techniques
- Hippocampus/metabolism
- Hippocampus/pathology
- Immunoblotting
- Immunohistochemistry
- Immunoprecipitation
- Intracellular Signaling Peptides and Proteins
- Ischemia/pathology
- LIM Domain Proteins
- Male
- Mice
- Microfilament Proteins
- Mixed Function Oxygenases
- Models, Genetic
- Molecular Sequence Data
- Mutation
- Nerve Growth Factor/metabolism
- Neurons/metabolism
- Neurons/pathology
- Oncogene Protein v-crk/metabolism
- PC12 Cells
- Phosphoproteins/biosynthesis
- Phosphoproteins/genetics
- Phosphorylation
- Protein Structure, Tertiary
- Rats
- Rats, Sprague-Dawley
- Retroviridae/genetics
- Reverse Transcriptase Polymerase Chain Reaction
- Sequence Homology, Amino Acid
- Transcription, Genetic
- Transfection
- Tyrosine/chemistry
- Up-Regulation
Collapse
Affiliation(s)
- Takahiro Sasaki
- Division of Clinical Immunology, Advanced Clinical Research Center, Institute of Medical Science, The University of Tokyo, Tokyo 108-8639, Japan
| | | | | | | | | | | | | | | | | |
Collapse
|
11
|
Huang Y, Magdaleno S, Hopkins R, Slaughter C, Curran T, Keshvara L. Tyrosine phosphorylated Disabled 1 recruits Crk family adapter proteins. Biochem Biophys Res Commun 2004; 318:204-12. [PMID: 15110774 DOI: 10.1016/j.bbrc.2004.04.023] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2004] [Indexed: 10/26/2022]
Abstract
Disabled 1 (Dab1) functions as a critical adapter protein in the Reelin signaling pathway to direct proper positioning of neurons during brain development. Reelin stimulates phosphorylation of Dab1 on tyrosines 198 and 220, and phosphorylated Dab1 is likely to interact with downstream signaling proteins that contain Src homology 2 (SH2) domains. To search for such proteins, we used a Sepharose-conjugated peptide containing phosphotyrosine 220 (PTyr-220) of Dab1, as an affinity matrix to capture binding proteins from mouse brain extracts. Mass spectrometric analysis of bound proteins revealed that Crk family adapter proteins selectively associated with this phosphorylation site. We further show that Crk-I and Crk-II, but not CrkL, stimulate phosphorylation of Dab1 on tyrosine 220 in a Src-dependent manner. Our results suggest that Crk family adapter proteins may play an important role in the Reelin signaling pathway during brain development.
Collapse
Affiliation(s)
- Yongcheng Huang
- Division of Pharmacology, College of Pharmacy, The Ohio State University, 500 W. 12th Avenue, Columbus, OH 43210, USA
| | | | | | | | | | | |
Collapse
|
12
|
Abstract
Trk receptors are a family of three receptor tyrosine kinases, each of which can be activated by one or more of four neurotrophins-nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and neurotrophins 3 and 4 (NT3 and NT4). Neurotrophin signaling through these receptors regulates cell survival, proliferation, the fate of neural precursors, axon and dendrite growth and patterning, and the expression and activity of functionally important proteins, such as ion channels and neurotransmitter receptors. In the adult nervous system, the Trk receptors regulate synaptic strength and plasticity. The cytoplasmic domains of Trk receptors contain several sites of tyrosine phosphorylation that recruit intermediates in intracellular signaling cascades. As a result, Trk receptor signaling activates several small G proteins, including Ras, Rap-1, and the Cdc-42-Rac-Rho family, as well as pathways regulated by MAP kinase, PI 3-kinase and phospholipase-C-gamma (PLC-gamma). Trk receptor activation has different consequences in different cells, and the specificity of downstream Trk receptor-mediated signaling is controlled through expression of intermediates in these signaling pathways and membrane trafficking that regulates localization of different signaling constituents. Perhaps the most fascinating aspect of Trk receptor-mediated signaling is its interplay with signaling promoted by the pan-neurotrophin receptor p75NTR. p75NTR activates a distinct set of signaling pathways within cells that are in some instances synergistic and in other instances antagonistic to those activated by Trk receptors. Several of these are proapoptotic but are suppressed by Trk receptor-initiated signaling. p75NTR also influences the conformations of Trk receptors; this modifies ligand-binding specificity and affinity with important developmental consequences.
Collapse
Affiliation(s)
- Eric J Huang
- Department of Pathology, University of California Veterans Administration Medical Center, San Francisco, California 94143, USA.
| | | |
Collapse
|
13
|
Scaife RM, Job D, Langdon WY. Rapid microtubule-dependent induction of neurite-like extensions in NIH 3T3 fibroblasts by inhibition of ROCK and Cbl. Mol Biol Cell 2003; 14:4605-17. [PMID: 12960437 PMCID: PMC266776 DOI: 10.1091/mbc.e02-11-0739] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
A number of key cellular functions, such as morphological differentiation and cell motility, are closely associated with changes in cytoskeletal dynamics. Many of the principal signaling components involved in actin cytoskeletal dynamics have been identified, and these have been shown to be critically involved in cell motility. In contrast, signaling to microtubules remains relatively uncharacterized, and the importance of signaling pathways in modulation of microtubule dynamics has so far not been established clearly. We report here that the Rho-effector ROCK and the multiadaptor proto-oncoprotein Cbl can profoundly affect the microtubule cytoskeleton. Simultaneous inhibition of these two signaling molecules induces a dramatic rearrangement of the microtubule cytoskeleton into microtubule bundles. The formation of these microtubule bundles, which does not involve signaling by Rac, Cdc42, Crk, phosphatidylinositol 3-kinase, and Abl, is sufficient to induce distinct neurite-like extensions in NIH 3T3 fibroblasts, even in the absence of microfilaments. This novel microtubule-dependent function that promotes neurite-like extensions is not dependent on net changes in microtubule polymerization or stabilization, but rather involves selective elongation and reorganization of microtubules into long bundles.
Collapse
Affiliation(s)
- Robin M Scaife
- Department of Pathology, University of Western Australia, Crawley, WA 6009, Australia.
| | | | | |
Collapse
|
14
|
Sakakibara A, Ohba Y, Kurokawa K, Matsuda M, Hattori S. Novel function of Chat in controlling cell adhesion via Cas-Crk-C3G-pathway-mediated Rap1 activation. J Cell Sci 2002; 115:4915-24. [PMID: 12432078 DOI: 10.1242/jcs.00207] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Chat (Cas/HEF1-associated signal transducer) is a novel signaling molecule with an N-terminal SH2 domain and C-terminal Cas/HEF1 association domain that is implicated in the regulation of cell adhesion. The Cas/HEF1 association domain also shows sequence similarity with guanine nucleotide exchange factors for Ras family small GTPases. In this study, we found significant activation of Rap1 in Chat-overexpressing cells. Myr-Chat, a membrane-targeted form of Chat, activated Rap1 more efficiently. Interestingly, Chat and Cas synergistically activated Rap1. Certain Cas, Crk or C3G mutants suppressed Rap1 activation by Chat. We also confirmed the ternary complex formation consisting of Chat, Cas and Crk. Thus, it is likely that Chat-induced Rap1 activation was mediated by upregulation of the Cas-Crk-C3G signaling pathway rather than direct guanine nucleotide exchange factor activity of Chat. We further demonstrated that Myr-Chat expression induced cell periphery spreading and cell shape branching and that this activity also depended on the Cas-Crk-C3G pathway and Rap1 activity. Moreover, expression of Myr-Chat enhanced integrin-mediated cell adhesion. Taken together we propose a novel role for the Chat-Cas complex in controlling cell adhesion via the activation of Rap1.
Collapse
Affiliation(s)
- Akira Sakakibara
- Division of Biochemistry and Cellular Biology, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Kodaira, Tokyo 187-8502, Japan.
| | | | | | | | | |
Collapse
|
15
|
Nishihara H, Maeda M, Oda A, Tsuda M, Sawa H, Nagashima K, Tanaka S. DOCK2 associates with CrkL and regulates Rac1 in human leukemia cell lines. Blood 2002; 100:3968-74. [PMID: 12393632 DOI: 10.1182/blood-2001-11-0032] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The CDM (ced-5 of Caenorhabditis elegans, DOCK180 [downstream of Crk with molecular weight of 180 kDa] of humans, and myoblast city of Drosophila melanogaster) family of proteins has been shown to play a pivotal role in the integrin-mediated signaling pathway under the regulation of an adaptor molecule c-CT10-related kinase II (c-Crk-II) in adherent cells. Recently, hematopoietic cell-specific CDM protein DOCK2 has been shown to be indispensable for lymphocyte migration. However, the regulatory mechanism for DOCK2 is still unknown because DOCK2 lacks a c-Crk-II binding consensus motif. In this study, we demonstrated that DOCK2 bound to CrkL, which is present exclusively in hematopoietic cells both in vivo and in vitro, and we also found that 2 separate regions of DOCK2 contributed to its binding to Src homology 3 (SH3) domain of CrkL. Colocalization of DOCK2 with Crk-like (CrkL) and F-actin was shown by immunocytochemical analysis with the use of Jurkat cells. We also found that CrkL-induced activation of small guanine triphosphatase (GTPase) Rac1 was significantly inhibited by the DOCK2-dCS mutant in 293T cells. Furthermore, the association of DOCK2 and Vav, the guanine-nucleotide exchanging factor (GEF) for Rac1, was demonstrated in Jurkat cells. Finally, the stable expression of DOCK2-dCS mutant in Jurkat cells was shown to reduce cell attachment. These data suggest the presence of a novel protein complex of CrkL, DOCK2, and Vav to regulate Rac1 in leukemia cell lines.
Collapse
Affiliation(s)
- Hiroshi Nishihara
- Laboratory of Molecular and Cellular Pathology, Hokkaido University School of Medicine, Sapporo, Japan
| | | | | | | | | | | | | |
Collapse
|
16
|
Nishihara H, Maeda M, Tsuda M, Makino Y, Sawa H, Nagashima K, Tanaka S. DOCK2 mediates T cell receptor-induced activation of Rac2 and IL-2 transcription. Biochem Biophys Res Commun 2002; 296:716-20. [PMID: 12176041 DOI: 10.1016/s0006-291x(02)00931-2] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
DOCK2, a CDM family protein exclusively found in hematopoietic cells, has been shown to play a role in lymphocyte migration by the regulation of actin cytoskeleton. Although DOCK2 has been shown to induce the activation of Rac1, the regulatory mechanism of Rac2, which is a hematopoietic cell-specific small GTPase, is still unknown. In this study, we examined the role of DOCK2 in the activation of Rac2 in hematopoietic cells. DOCK2 was found to associate with the zeta subunit of the CD3 complex of T cell receptors in Jurkat cells and to activate forced expressed Rac2 in 293T cells. In addition, the stable expression of DOCK2 in Jurkat cells exhibited the elevated activity of endogenous Rac2. Furthermore, the transcriptional activity of interleukin-2 (IL-2) was enhanced in DOCK2-expressing Jurkat cells and the dominant negative form of Rac2 suppressed its elevated IL-2 promoter activity. These results suggest that DOCK2 mediates TCR-dependent activation of Rac2, leading to the regulation of IL-2 promoter activity in T cells.
Collapse
Affiliation(s)
- Hiroshi Nishihara
- Laboratory of Molecular and Cellular Pathology, Hokkaido University School of Medicine, N 15, W7, Kita-ku, Sapporo 060-8638, Japan
| | | | | | | | | | | | | |
Collapse
|
17
|
Goel HL, Dey CS. PKC-regulated myogenesis is associated with increased tyrosine phosphorylation of FAK, Cas, and paxillin, formation of Cas-CRK complex, and JNK activation. Differentiation 2002; 70:257-71. [PMID: 12190987 DOI: 10.1046/j.1432-0436.2002.700604.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Previous reports suggest that PKC plays an important role in regulating myogenesis. However, the regulatory signaling pathways are not fully understood. We examined the effects of PKC downregulation on signaling events during skeletal muscle differentiation. We found that downregulation of PKC results in increased myogenesis in C2C12 cells as measured by creatine kinase activity and myogenin expression. We showed that, during differentiation, downregulation of PKC expression results in increased tyrosine phosphorylation of FAK, Cas, and paxillin, concomitant with enhanced Cas-CrkII complex formation, which leads to activation of JNK2. But in proliferated muscle cells, PKC inhibition results in FAK and Cas tyrosine dephosphorylation. Further, disruption of actin cytoskeleton by cytochalasin D prevents the activation of FAK and Cas as well as the formation of Cas-CrkII complex stimulated by PKC downregulation during muscle cell differentiation. Finally, we observed that PKC downregulation increases the tyrosine phosphorylation of focal adhesion associated proteins. Based on the above data, we propose that PKC downregulation results in enhanced tyrosine phosphorylation of FAK, Cas, and paxillin, thus promoting the establishment of Cas-CrkII complex, leading to activation of JNK and that these interactions are dependent upon the integrity of actin cytoskeleton during muscle cell differentiation. Data presented here significantly contribute to elucidating the regulatory role of PKC in myogenesis possibly through integrin signaling pathway.
Collapse
Affiliation(s)
- Hira Lal Goel
- Signal Transduction Research Laboratory, Department of Biotechnology, National Institute of Pharmaceutical Education and Research, India
| | | |
Collapse
|
18
|
Cho SY, Klemke RL. Purification of pseudopodia from polarized cells reveals redistribution and activation of Rac through assembly of a CAS/Crk scaffold. J Cell Biol 2002; 156:725-36. [PMID: 11839772 PMCID: PMC2174083 DOI: 10.1083/jcb.200111032] [Citation(s) in RCA: 152] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Initiation of cell migration requires morphological polarization with formation of a dominant leading pseudopodium and rear compartment. A molecular understanding of this process has been limited, due to the inability to biochemically separate the leading pseudopodium from the rear of the cell. Here we examine the spatio-temporal localization and activation of cytoskeletal-associated signals in purified pseudopodia directed to undergo growth or retraction. Pseudopodia growth requires assembly of a p130Crk-associated substrate (CAS)/c-CrkII (Crk) scaffold, which facilitates translocation and activation of Rac1. Interestingly, Rac1 activation then serves as a positive-feedback loop to maintain CAS/Crk coupling and pseudopodia extension. Conversely, disassembly of this molecular scaffold is critical for export and down regulation of Rac1 activity and induction of pseudopodia retraction. Surprisingly, the uncoupling of Crk from CAS during pseudopodium retraction is independent of changes in focal adhesion kinase activity and CAS tyrosine phosphorylation. These findings establish CAS/Crk as an essential scaffold for Rac1-mediated pseudopodia growth and retraction, and illustrate spatio-temporal segregation of cytoskeletal signals during cell polarization.
Collapse
Affiliation(s)
- Samuel Y Cho
- Department of Immunology, The Scripps Research Institute, La Jolla, CA 92037, USA
| | | |
Collapse
|
19
|
Abstract
Crk family adaptors are widely expressed and mediate the timely formation of signal transduction protein complexes upon a variety of extracellular stimuli, including various growth and differentiation factors. Selective formation of multi-protein complexes by the Crk and Crk-like (CRKL) proteins depends on specific motifs recognized by their SH2 and SH3 domains. In the case of the first SH3 domains [SH3(1)] a P-x-x-P-x-K motif is crucial for highly selective binding, while the SH2 domains prefer motifs which conform to the consensus pY-x-x-P. Crk family proteins are involved in the relocalization and activation of several different effector proteins which include guanine nucleotide releasing proteins like C3G, protein kinases of the Abl- and GCK-families and small GTPases like Rap1 and Rac. Crk-type proteins have been found not only in vertebrates but also in flies and nematodes. Major insight into the function of Crk within organisms came from the genetic model organism C. elegans, where the Crk-homologue CED-2 regulates cell engulfment and phagocytosis. Other biological outcomes of the Crk-activated signal transduction cascades include the modulation of cell adhesion, cell migration and immune cell responses. Crk family adaptors also appear to play a role in mediating the action of human oncogenes like the leukaemia-inducing Bcr-Abl protein. This review summarizes some key findings and highlights recent insights and open questions.
Collapse
Affiliation(s)
- S M Feller
- Cell Signalling Laboratory, Imperial Cancer Research Fund, University of Oxford, Institute of Molecular Medicine, John Radcliffe Hospital, Headington, Oxford OX3 9DS, UK.
| |
Collapse
|
20
|
Gelkop S, Babichev Y, Isakov N. T cell activation induces direct binding of the Crk adapter protein to the regulatory subunit of phosphatidylinositol 3-kinase (p85) via a complex mechanism involving the Cbl protein. J Biol Chem 2001; 276:36174-82. [PMID: 11418612 DOI: 10.1074/jbc.m100731200] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Crk adapter proteins are assumed to play a role in T lymphocyte activation because of their induced association with tyrosine-phosphorylated proteins, such as ZAP-70 and Cbl, and with the phosphatidylinositol 3kinase regulatory subunit, p85, following engagement of the T cell antigen receptor. Although the exact mechanism of interaction between these molecules has not been fully defined, it has been generally accepted that Crk, ZAP-70, and p85 interact with tyrosine-phosphorylated Cbl, which serves as a major scaffold protein in activated T lymphocytes. Our present results demonstrate a cell activation-dependent reciprocal co-immunoprecipitation of CrkII and p85 from lysates of Jurkat T cells and a direct binding of CrkII to p85 in an overlay assay. The use of bead-immobilized GST fusion proteins indicated a complex mechanism of interaction between CrkII and p85 involving two distinct and mutually independent regions in each molecule. A relatively high affinity binding of the CrkII-SH3(N) domain to p85 and the p85-proline-B cell receptor-proline (PBP) region to CrkII was observed in lysates of either resting or activated T cells. Direct physical interaction between the CrkII-SH3(N) and the p85-PBP domain was demonstrated using recombinant fusion proteins and was further substantiated by binding competition studies. In addition, immobilized fusion proteins possessing the CrkII-SH2 and p85-SH3 domains were found to pull down p85 and CrkII, respectively, but only from lysates of activated T cells. Nevertheless, the GST-CrkII-SH2 fusion protein was unable to mediate direct association with p85 from lysates of either resting or activated T cells. Our results support a model in which T cell activation dependent conformational changes in CrkII and/or p85 promote an initial direct or indirect low affinity interaction between the two molecules, which is then stabilized by a secondary high affinity interaction mediated by direct binding of the CrkII-SH3(N) to the p85-PBP domain.
Collapse
Affiliation(s)
- S Gelkop
- Department of Microbiology and Immunology, Faculty of Health Sciences, and the Cancer Research Center, Ben Gurion University of the Negev, Beer Sheva 84105, Israel
| | | | | |
Collapse
|
21
|
Kao S, Jaiswal RK, Kolch W, Landreth GE. Identification of the mechanisms regulating the differential activation of the mapk cascade by epidermal growth factor and nerve growth factor in PC12 cells. J Biol Chem 2001; 276:18169-77. [PMID: 11278445 DOI: 10.1074/jbc.m008870200] [Citation(s) in RCA: 295] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In PC12 cells, epidermal growth factor (EGF) transiently stimulates the mitogen-activated protein (MAP) kinases, ERK1 and ERK2, and provokes cellular proliferation. In contrast, nerve growth factor (NGF) stimulation leads to the sustained activation of the MAPKs and subsequently to neuronal differentiation. It has been shown that both the magnitude and longevity of MAPK activation governs the nature of the cellular response. The activations of MAPKs are dependent upon two distinct small G-proteins, Ras and Rap1, that link the growth factor receptors to the MAPK cascade by activating c-Raf and B-Raf, respectively. We found that Ras was transiently stimulated upon both EGF and NGF treatment of PC12 cells. However, EGF transiently activated Rap1, whereas NGF stimulated prolonged Rap1 activation. The activation of the ERKs was due almost exclusively (>90%) to the action of B-Raf. The transient activation of the MAPKs by EGF was a consequence of the formation of a short lived complex assembling on the EGF receptor itself, composed of Crk, C3G, Rap1, and B-Raf. In contrast, NGF stimulation of the cells resulted in the phosphorylation of FRS2. FRS2 scaffolded the assembly of a stable complex of Crk, C3G, Rap1, and B-Raf resulting in the prolonged activation of the MAPKs. Together, these data provide a signaling link between growth factor receptors and MAPK activation and a mechanistic explanation of the differential MAPK kinetics exhibited by these growth factors.
Collapse
Affiliation(s)
- S Kao
- Department of Neurosciences and the Alzheimer Research Laboratory, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106, USA
| | | | | | | |
Collapse
|
22
|
Bruce-Staskal PJ, Bouton AH. PKC-dependent activation of FAK and src induces tyrosine phosphorylation of Cas and formation of Cas-Crk complexes. Exp Cell Res 2001; 264:296-306. [PMID: 11262186 DOI: 10.1006/excr.2000.5137] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
SH-SY5Y neuroblastoma cells are a well-characterized model for studying the induction of neuronal differentiation. TPA treatment of these cells induces cytoskeletal rearrangements that ultimately result in neurite extension. However, the signaling pathways that precede these changes are poorly understood. Other investigators have shown that TPA treatment of SH-SY5Y cells results in increased tyrosine phosphorylation of cytoskeletal-associated proteins, including the adapter protein Cas. In this report, we examine the events upstream and downstream of Cas phosphorylation. We show that TPA treatment induces the PKC-dependent association of tyrosine-phosphorylated Cas with Crk. The activity of two protein tyrosine kinases, Src and FAK, was shown to be necessary and sufficient for TPA-induced Cas phosphorylation. We propose that the PKC-dependent phosphorylation of Cas by Src and FAK promotes the establishment of Cas-Crk complexes and that these interactions may play an important role in regulating the actin cytoskeleton during neuronal differentiation.
Collapse
Affiliation(s)
- P J Bruce-Staskal
- Department of Microbiology, University of Virginia School of Medicine, Charlottesville, Virginia, 22908-0734, USA
| | | |
Collapse
|
23
|
Abstract
Neurotrophins regulate development, maintenance, and function of vertebrate nervous systems. Neurotrophins activate two different classes of receptors, the Trk family of receptor tyrosine kinases and p75NTR, a member of the TNF receptor superfamily. Through these, neurotrophins activate many signaling pathways, including those mediated by ras and members of the cdc-42/ras/rho G protein families, and the MAP kinase, PI-3 kinase, and Jun kinase cascades. During development, limiting amounts of neurotrophins function as survival factors to ensure a match between the number of surviving neurons and the requirement for appropriate target innervation. They also regulate cell fate decisions, axon growth, dendrite pruning, the patterning of innervation and the expression of proteins crucial for normal neuronal function, such as neurotransmitters and ion channels. These proteins also regulate many aspects of neural function. In the mature nervous system, they control synaptic function and synaptic plasticity, while continuing to modulate neuronal survival.
Collapse
Affiliation(s)
- Eric J Huang
- Department of Pathology, University of California, San Francisco, California 94143; e-mail:
| | - Louis F Reichardt
- Department of Physiology, University of California, San Francisco, California 94143, and Howard Hughes Medical Institute, San Francisco, California 94143; e-mail:
| |
Collapse
|
24
|
Weidow CL, Black DS, Bliska JB, Bouton AH. CAS/Crk signalling mediates uptake of Yersinia into human epithelial cells. Cell Microbiol 2000; 2:549-60. [PMID: 11207607 DOI: 10.1046/j.1462-5822.2000.00079.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Uptake of Yersinia pseudotuberculosis into mammalian cells involves engagement of beta1 integrin receptors by the bacterial protein invasin. This triggers a host response that involves tyrosine phosphorylation of proteins and the induction of actin rearrangements that lead to cellular uptake of bacteria. In this report, we show that the focal adhesion protein CAS plays an important role in Yersinia uptake, and that its function is linked to the phosphorylation-dependent interaction between CAS and Crk. These studies demonstrate that Yersinia binding to host cell receptors initiates a cascade of events involving tyrosine phosphorylation of CAS, subsequent formation of functional CAS-Crk complexes and the activity of the small GTP-binding protein Rac1. The delineation of this pathway lends support for a model in which Yersinia uptake into human epithelial cells is dependent upon aspects of host signalling pathways that govern actin cytoskeleton remodelling and cell migration.
Collapse
Affiliation(s)
- C L Weidow
- Department of Microbiology and Cancer Center, University of Virginia Health System, Charlottesville 22908-0734, USA
| | | | | | | |
Collapse
|
25
|
Lu L, Annerén C, Reedquist KA, Bos JL, Welsh M. NGF-Dependent neurite outgrowth in PC12 cells overexpressing the Src homology 2-domain protein shb requires activation of the Rap1 pathway. Exp Cell Res 2000; 259:370-7. [PMID: 10964504 DOI: 10.1006/excr.2000.4984] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The Src homology 2 (SH2) domain adaptor protein Shb has been shown to transmit NGF- and FGF-2-dependent differentiation signals in PC12 cells. To study if this involves signaling through the small GTPase Rap1, Rap1 activity was assessed in Shb-overexpressing PC12 cells. We demonstrate that NGF and EGF induce Rap1 activation in PC12-Shb cells, while FGF-2 fails to do so. However, PC12 cells expressing Shb with an inactivated SH2 domain do not respond to NGF stimulation with Rap1 activation. The CrkII SH2 domain interacts with Shb and a 130- to 135-kDa phosphotyrosine protein present mainly in PC12-Shb cells and these interactions may thus relate to the effect of Shb on Rap1 activation. Transient expression of RalGDS-RBD or Rap1GAP to block the Rap1 pathway reduces the NGF-dependent neurite outgrowth in PC12-Shb cells. These results suggest a role of Shb in NGF-dependent Rap1 signaling and this pathway may be of significance for neurite outgrowth under certain conditions.
Collapse
Affiliation(s)
- L Lu
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | | | | | | | | |
Collapse
|
26
|
Annerén C, Reedquist KA, Bos JL, Welsh M. GTK, a Src-related tyrosine kinase, induces nerve growth factor-independent neurite outgrowth in PC12 cells through activation of the Rap1 pathway. Relationship to Shb tyrosine phosphorylation and elevated levels of focal adhesion kinase. J Biol Chem 2000; 275:29153-61. [PMID: 10878015 DOI: 10.1074/jbc.m003926200] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The rat pheochromocytoma cell line PC12 is extensively used as a model for studies of neuronal cell differentiation. These cells develop a sympathetic neuron-like phenotype when cultured in the presence of nerve growth factor. The present study was performed in order to assess the role of mouse GTK (previously named BSK/IYK), a cytoplasmic tyrosine kinase belonging to the Src family, for neurite outgrowth in PC12 cells. We report that PC12 cells stably overexpressing GTK exhibit a larger fraction of cells with neurites as compared with control cells, and this response is not accompanied by an increased ERK activity. Treatment of the cells with the MEK inhibitor PD98059 did not reduce the GTK-dependent increased in neurite outgrowth. GTK expression induces a nerve growth factor-independent Rap1 activation, probably through altered CrkII signaling. We observe increased CrkII complex formation with p130(Cas), focal adhesion kinase (FAK), and Shb in PC12-GTK cells. The expression of GTK also correlates with a markedly increased content of FAK, phosphorylation of the adaptor protein Shb, and an association between these two proteins. Transient transfection of GTK-overexpressing cells with RalGDS-RBD or Rap1GAP, inhibitors of the Rap1 pathway, reduces the GTK-dependent neurite outgrowth. These data suggest that GTK participates in a signaling pathway, perhaps involving Shb, FAK and Rap1, that induces neurite outgrowth in PC12 cells.
Collapse
Affiliation(s)
- C Annerén
- Department of Medical Cell Biology, Uppsala University, Uppsala 751 23, Sweden
| | | | | | | |
Collapse
|
27
|
Garcia-Guzman M, Larsen E, Vuori K. The proto-oncogene c-Cbl is a positive regulator of Met-induced MAP kinase activation: a role for the adaptor protein Crk. Oncogene 2000; 19:4058-65. [PMID: 10962563 DOI: 10.1038/sj.onc.1203750] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Hepatocyte growth factor triggers a complex biological program leading to invasive cell growth by activating the c-Met receptor tyrosine kinase. Following activation, Met signaling is elicited via its interactions with SH2-containing proteins, or via the phosphorylation of the docking protein Gab1, and the subsequent interaction of Gab1 with additional SH2-containing effector molecules. We have previously shown that the interaction between phosphorylated Gab1 and the adaptor protein Crk mediates activation of the JNK pathway downstream of Met. We report here that c-Cbl, which is a Gab1-like docking protein, also becomes tyrosine-phosphorylated in response to Met activation and serves as a docking molecule for various SH2-containing molecules, including Crk. We further show that Cbl is similarly capable of enhancing Met-induced JNK activation, and several lines of experimentation suggests that it does so by interacting with Crk. We also show that both Cbl and Gab1 enhance Met-induced activation of another MAP kinase cascade, the ERK pathway, in a Crk-independent manner. Taken together, our studies demonstrate a previously unidentified functional role for Cbl in Met signaling and suggest that Met utilizes at least two docking proteins, Gab1 and Cbl, to activate downstream signaling pathways. Oncogene (2000) 19, 4058 - 4065.
Collapse
Affiliation(s)
- M Garcia-Guzman
- Cancer Research Center, The Burnham Institute, 10901 North Torrey Pines Road, La Jolla, California, CA 92037, USA
| | | | | |
Collapse
|
28
|
Ishino M, Aoto H, Sasaski H, Suzuki R, Sasaki T. Phosphorylation of Hic-5 at tyrosine 60 by CAKbeta and Fyn. FEBS Lett 2000; 474:179-83. [PMID: 10838081 DOI: 10.1016/s0014-5793(00)01597-0] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Hic-5 is a CAKbeta-binding protein localized at focal adhesions. Here we show that overexpression of CAKbeta or Fyn, but not FAK, enhanced the tyrosine phosphorylation of coexpressed Hic-5 in COS-7 cells. These phosphorylations were further augmented by stimulating cells with osmotic stress. The Y60F mutant of Hic-5 was not phosphorylated, and Hic-5 phosphorylated on tyrosine 60 was bound specifically to the SH2 domain of Csk. Coexpression experiments revealed that the phosphorylation of Hic-5 by CAKbeta required the kinase activation of CAKbeta and binding of Hic-5 by CAKbeta. Specific phosphorylation of Hic-5 by CAKbeta and Fyn may activate a signaling pathway mediated by Hic-5.
Collapse
Affiliation(s)
- M Ishino
- Department of Biochemistry, Cancer Research Institute, Sapporo Medical University School of Medicine, South-1, West-17, Chuo-Ku, 060-8556, Sapporo, Japan
| | | | | | | | | |
Collapse
|
29
|
Posern G, Saffrich R, Ansorge W, Feller SM. Rapid lamellipodia formation in nerve growth factor-stimulated PC12 cells is dependent on Rac and PI3K activity. J Cell Physiol 2000; 183:416-24. [PMID: 10797317 DOI: 10.1002/(sici)1097-4652(200006)183:3<416::aid-jcp15>3.0.co;2-r] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Neuronal differentiation of PC12 cells is achieved by stimulation with nerve growth factor (NGF) but not by epidermal growth factor (EGF). However, features of differentiation such as neurite outgrowth are observable at the earliest after several hours. Using actin staining of the cells, we show here that NGF stimulation leads to lamellipodia formation within only 3 min at the periphery of the PC12 cells. EGF stimulation or microinjection of differentiation-inducing c-Crk I protein does not cause lamellipodia. The actin reorganization after NGF stimulation is blocked by microinjecting dominant negative Rac protein. The lamellipodia formation is also abolished by inhibitors of phosphatidylinositol 3-kinase, wortmannin and LY 294002 in a concentration-dependent manner. Phase-contrast time-lapse microscopy was used to analyze membrane dynamics in real time and to confirm the induction of lamellipodia by NGF and their inhibition by pretreatment with both wortmannin and LY 294002. The results indicate that NGF, but not EGF, leads to rapid lamellipodia formation in PC12 cells via phosphatidylinositol 3-kinase and the small GTPase Rac, thereby defining a novel role for these factors in early NGF signaling.
Collapse
Affiliation(s)
- G Posern
- Institut für Medizinische Strahlenkunde und Zellforschung (MSZ), Julius-Maximilians-University, Würzburg, Germany.
| | | | | | | |
Collapse
|
30
|
Buensuceso CS, O'Toole TE. The association of CRKII with C3G can be regulated by integrins and defines a novel means to regulate the mitogen-activated protein kinases. J Biol Chem 2000; 275:13118-25. [PMID: 10777617 DOI: 10.1074/jbc.275.17.13118] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
In studies to define mechanisms of ERK activation in Chinese hamster ovary cells, we have observed an inverse correlation between CRKII-C3G complex formation and ERK activity. That is, we were able to coprecipitate the guanine nucleotide exchange factor C3G with the adaptor protein CRKII in lysates from suspended cells that had low ERK activity, but we could not do so or could do so less efficiently in lysates of adherent cells with increased ERK activity. Consistent with the presence of a functional CRKII-C3G complex, we detected more GTP-loaded RAP1 in suspension than adherent lysates. Overexpression of cDNAs encoding B-RAF, CRKII W109L, and PTP1B C215S activated ERK in suspension cells, the latter two constructs also disrupting CRKII-C3G complex formation. Finally, we have also observed that certain integrin alpha subunit cytoplasmic splice variants differentially regulate ERK1/2 but also in a manner that correlated with levels of a CRKII-C3G complex. Thus, these data suggest the involvement of integrins in an ERK suppression pathway mediated by CRKII-C3G complex formation and downstream signaling from activated RAP1.
Collapse
Affiliation(s)
- C S Buensuceso
- Department of Vascular Biology, The Scripps Research Institute, La Jolla, California 92037, USA
| | | |
Collapse
|
31
|
Cho SY, Klemke RL. Extracellular-regulated kinase activation and CAS/Crk coupling regulate cell migration and suppress apoptosis during invasion of the extracellular matrix. J Cell Biol 2000; 149:223-36. [PMID: 10747099 PMCID: PMC2175095 DOI: 10.1083/jcb.149.1.223] [Citation(s) in RCA: 222] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Regulation of cell migration/invasion is important for embryonic development, immune function, and angiogenesis. However, migratory cells must also coordinately activate survival mechanisms to invade the extracellular matrix and colonize foreign sites in the body. Although invasive cells activate protective programs to survive under diverse and sometimes hostile conditions, the molecular signals that regulate these processes are poorly understood. Evidence is provided that signals that induce cell invasion also promote cell survival by suppressing apoptosis of migratory cells. Extracellular-regulated kinase (ERK) activation and molecular coupling of the adaptor proteins p130 Crk-associated substrate (CAS) and c-CrkII (Crk) represent two distinct pathways that induce cell invasion and protect cells from apoptosis in a three-dimensional collagen matrix. CAS/Crk-mediated cell invasion and survival requires activation of the small GTPase Rac, whereas ERK-induced cell invasion, but not survival requires myosin light chain kinase activation and myosin light chain phosphorylation. Uncoupling CAS from Crk or inhibition of ERK activity prevents migration and induces apoptosis of invasive cells. These findings provide molecular evidence that during invasion of the extracellular matrix, cells coordinately regulate migration and survival mechanisms through ERK activation and CAS/Crk coupling.
Collapse
Affiliation(s)
- Samuel Y. Cho
- Department of Immunology, The Scripps Research Institute, La Jolla, California 92037
| | - Richard L. Klemke
- Department of Immunology, The Scripps Research Institute, La Jolla, California 92037
| |
Collapse
|
32
|
Matsumoto T, Yokote K, Take A, Takemoto M, Asaumi S, Hashimoto Y, Matsuda M, Saito Y, Mori S. Differential interaction of CrkII adaptor protein with platelet-derived growth factor alpha- and beta-receptors is determined by its internal tyrosine phosphorylation. Biochem Biophys Res Commun 2000; 270:28-33. [PMID: 10733900 DOI: 10.1006/bbrc.2000.2374] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
CrkII is an intracellular adaptor protein involved in signal transduction by various growth factors. Activation of PDGF alpha-receptor resulted in its association with CrkII in vivo. In contrast, binding of CrkII to the PDGF beta-receptor was negligible, despite its becoming prominently phosphorylated. Bacterially expressed GST-CrkII SH2 domain specifically bound to Tyr-762 and Tyr-771 in the activated PDGF alpha- and beta- receptors, respectively. GST fusion protein of full-length CrkII also bound to the activated PDGF beta-receptor. However, tyrosine phosphorylation of GST-CrkII diminished its binding to the beta-receptor. CrkI, a truncated version of CrkII lacking the phosphorylatable tyrosine residue, could bind to both PDGF alpha- and beta-receptors in vivo. In conclusion, tyrosine phosphorylation of CrkII negatively affects its binding to the PDGF receptors. The differential binding of CrkII to the PDGF alpha- and beta- receptors may be a rationale for functional diversity between the two receptors.
Collapse
Affiliation(s)
- T Matsumoto
- Second Department of Internal Medicine, Chiba University School of Medicine, 1-8-1 Inohana, Chuo-ku, Chiba, 260-0856, Japan
| | | | | | | | | | | | | | | | | |
Collapse
|
33
|
Abstract
Nerve growth factor (NGF) initiates the majority of its biological effects by promoting the dimerization and activation of the tyrosine kinase receptor TrkA. In addition to rapid increases in the phosphorylation of phosphatidylinositol 3'-kinase (PI 3-kinase) and phospholipase C-gamma and increased ras activity, phosphorylation of c-Crk and paxillin proteins has been observed upon TrkA activation. The c-Abl tyrosine kinase is involved in the control of the axonal cytoskeleton and is known to interact with c-Crk proteins. Here we have tested the possibility that TrkA receptors might form an association with the c-Abl protein. After transfection in 293T cells, TrkA and c-Abl kinases could be coimmunoprecipitated. This interaction did not require TrkA receptors to be autophosphorylated. Mapping analysis indicated that the region of c-Abl association was confined to the juxtamembrane region of TrkA. The interaction of c-Abl with TrkA was also observed in differentiated pheochromocytoma PC12 cells. These results suggest that c-Abl may be recruited to the NGF receptor complex and be involved in regulating specific phosphorylation events that occur during neuronal differentiation.
Collapse
Affiliation(s)
- H Yano
- Molecular Neurobiology Program, Skirball Institute of Biomolecular Medicine, New York University School of Medicine, New York, NY 10016, USA
| | | | | | | | | |
Collapse
|
34
|
Garcia-Guzman M, Dolfi F, Zeh K, Vuori K. Met-induced JNK activation is mediated by the adapter protein Crk and correlates with the Gab1 - Crk signaling complex formation. Oncogene 1999; 18:7775-86. [PMID: 10618718 DOI: 10.1038/sj.onc.1203198] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Constitutive activation of the Met tyrosine kinase results in transformation of cells of diverse origin. Recent studies have demonstrated a role for the c-Jun N-terminal kinase (JNK) in Met-induced transformation, but little is known about the molecular mechanisms that connect Met to JNK activation. Our studies show that activated Met associates with, and phosphorylates, the docking protein Gab1, which in turn binds to the src homology 2 (SH2)-domain of the adapter protein Crk and recruits Crk to the Met signaling complex. Formation of the Gab1 - Crk complex correlates with Met-induced JNK activation, and mutant forms of Met that fail to induce the complex formation also fail to activate JNK. Importantly, expression of a loss-of-function mutant of Crk severely impairs activation of the JNK pathway by Met. We also show here that Met controls the transcription of the matrix metalloproteinase-1 (MMP-1) gene in carcinoma cells and that this transcriptional regulation occurs in a Crk - JNK-dependent manner through an AP-1 element in the MMP-1 promoter. Taken together, our data implicate the Gab1 - Crk signaling complex in Met-induced JNK activation and suggest that the Gab1 - Crk complex formation may be an important event in regulating the tumorigenic phenotype of Met-transformed cells.
Collapse
Affiliation(s)
- M Garcia-Guzman
- Cancer Research Center, The Burnham Institute, 10901 North Torrey Pines Road, La Jolla, California, CA 92037, USA
| | | | | | | |
Collapse
|
35
|
Miyazaki K, Senga T, Matsuda S, Tanaka M, Machida K, Takenouchi Y, Nimura Y, Hamaguchi M. Critical amino acid substitutions in the Src SH3 domain that convert c-Src to be oncogenic. Biochem Biophys Res Commun 1999; 263:759-64. [PMID: 10512753 DOI: 10.1006/bbrc.1999.1464] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The Src homology 3 (SH3) domain, originally identified in v-Crk, plays an important role in signal transduction. The comparative study with c-src has revealed that v-src oncogene of Schmidt-Ruppin strain of Rous sarcoma virus has three point mutations in its SH3 domain and one in the upstream of SH3. To assess the role of these mutations, each of the single mutations was introduced into c-Src by oligonucleotide-directed mutagenesis and its effect on cell transformation was examined. While variant Src proteins that carry each one of single mutations could not transform cells, double mutation at positions 95 and 117 converted c-Src to be oncogenic and active in kinase. An additional mutation at position 124 together with one at 95 and 117 further activated Src kinase. By use of GST-fusion forms of v-Src SH3 and c-Src SH3, we found that these mutations in SH3 suppressed the binding of SH3 with c-Src protein, possibly with a linker region, while v-SrcSH3 retained the ability to bind a subset of cellular protein to the level similar to those of c-SrcSH3. Taken together, our results suggest that point mutations accumulated in SH3 region can activate, in concert, Src kinase by relaxing the interaction between SH3 and the linker region and subsequently convert Src to be oncogenic.
Collapse
Affiliation(s)
- K Miyazaki
- First Department of Surgery, Nagoya University School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya, 466-8550, Japan
| | | | | | | | | | | | | | | |
Collapse
|
36
|
Katayama H, Hashimoto Y, Kiyokawa E, Nakaya M, Sakamoto A, Machinami R, Kurata T, Mochizuki N, Matsuda M. Epidermal growth factor-dependent dissociation of CrkII proto-oncogene product from the epidermal growth factor receptor in human glioma cells. Jpn J Cancer Res 1999; 90:1096-103. [PMID: 10595738 PMCID: PMC5926002 DOI: 10.1111/j.1349-7006.1999.tb00683.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Human glioma cells frequently overexpress epidermal growth factor receptor (EGFR). We found that the CrkII proto-oncogene product was associated with the EGFR in human glioma cells in the absence of epidermal growth factor (EGF). EGF stimulation of glioma cells induced the phosphorylation of tyrosine 221 of the CrkII protein, which correlates with its dissociation from the EGFR. By contrast, Shc and Grb2 were inducibly associated with the EGFR in response to EGF stimulation of glioma cells. In A431 cells, epidermoid carcinoma cells which overexpress EGFR, CrkII was tyrosine-phosphorylated and associated with the EGFR in an EGF-dependent manner. Therefore, the dissociation of CrkII from the EGFR upon stimulation with EGF appears to be specific to glioma cells. The Cbl oncogene product was also tyrosine-phosphorylated in U87MG glioma cells upon EGF stimulation. However, unlike in other cell lines, CrkII was not inducibly bound to Cbl in U87MG glioma cells. Thus, EGF-dependent binding of CrkII to phosphotyrosine-containing proteins appears to be suppressed in glioma cells. To evaluate the physiological role of dissociation of CrkII from EGFR, we expressed the CrkII-23 mutant in glioma cells. CrkII-23 mutant, which was isolated as a suppressor gene of the EGF-dependent transformation of NRK cells, binds constitutively to EGFR. We found that expression of CrkII-23 inhibited the anchorage-independent growth of the glioma cells in the presence of EGF. Taken together, these data implicate EGF-dependent dissociation of CrkII from EGFR in the oncogenicity of human glioma cells.
Collapse
Affiliation(s)
- H Katayama
- Department of Pathology, National Institute of Infectious Diseases, Tokyo
| | | | | | | | | | | | | | | | | |
Collapse
|
37
|
Cheresh DA, Leng J, Klemke RL. Regulation of cell contraction and membrane ruffling by distinct signals in migratory cells. J Cell Biol 1999; 146:1107-16. [PMID: 10477763 PMCID: PMC2169492 DOI: 10.1083/jcb.146.5.1107] [Citation(s) in RCA: 212] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/1999] [Accepted: 07/23/1999] [Indexed: 01/19/2023] Open
Abstract
Cell migration and wound contraction requires assembly of actin into a functional myosin motor unit capable of generating force. However, cell migration also involves formation of actin-containing membrane ruffles. Evidence is provided that actin-myosin assembly and membrane ruffling are regulated by distinct signaling pathways in the migratory cell. Interaction of cells with extracellular matrix proteins or cytokines promote cell migration through activation of the MAP kinases ERK1 and ERK2 as well as the molecular coupling of the adaptor proteins p130CAS and c-CrkII. ERK signaling is independent of CAS/Crk coupling and regulates myosin light chain phosphorylation leading to actin-myosin assembly during cell migration and cell-mediated contraction of a collagen matrix. In contrast, membrane ruffling, but not cell contraction, requires Rac GTPase activity and the formation of a CAS/Crk complex that functions in the context of the Rac activating protein DOCK180. Thus, during cell migration ERK and CAS/Crk coupling operate as components of distinct signaling pathways that control actin assembly into myosin motors and membrane ruffles, respectively.
Collapse
Affiliation(s)
- David A. Cheresh
- Departments of Immunology and Vascular Biology, The Scripps Research Institute, La Jolla, California 92037
| | - Jie Leng
- Departments of Immunology and Vascular Biology, The Scripps Research Institute, La Jolla, California 92037
| | - Richard L. Klemke
- Departments of Immunology and Vascular Biology, The Scripps Research Institute, La Jolla, California 92037
| |
Collapse
|
38
|
Larsson H, Klint P, Landgren E, Claesson-Welsh L. Fibroblast growth factor receptor-1-mediated endothelial cell proliferation is dependent on the Src homology (SH) 2/SH3 domain-containing adaptor protein Crk. J Biol Chem 1999; 274:25726-34. [PMID: 10464310 DOI: 10.1074/jbc.274.36.25726] [Citation(s) in RCA: 89] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Stimulation of fibroblast growth factor receptor-1 (FGFR-1) expressed on endothelial cells leads to cellular migration and proliferation. We have examined the role of the Src homology (SH) 2/SH3 domain-containing adaptor protein Crk in these processes. Transient tyrosine phosphorylation of Crk in fibroblast growth factor-2-stimulated endothelial cells was dependent on the juxtamembrane tyrosine residue 463 in FGFR-1, and a Crk SH2 domain precipitated FGFR-1 via phosphorylated Tyr-463, indicating direct complex formation between Crk and FGFR-1. Furthermore, Crk SH2 and SH3 domains formed ligand-independent complexes with Shc, C3G, and the Crk-associated substrate (Cas). Tyrosine phosphorylation of C3G and Cas increased as a consequence of growth factor treatment. We examined the role of Crk in FGFR-1-mediated cellular responses by use of cells expressing chimeric platelet-derived growth factor receptor-alpha/FGFR-1 (alphaR/FR) wild type and mutant Y463F receptors. The kinase activity of alphaR/FR Y463F was intact, but both Crk and the adaptor FRS-2 were no longer tyrosine-phosphorylated in the mutant cells. Both wild type and mutant receptor cells migrated efficiently, whereas cells expressing the mutant alphaR/FR Y463F failed to proliferate and Erk2 and Jun kinase activities were suppressed in these cells. In wild type alphaR/FR cells transiently expressing an SH2 domain mutant of Crk, Erk and Jun kinase activities as well as DNA synthesis were attenuated. Our data indicate that Crk participates in signaling complexes downstream of FGFR-1, which propagate mitogenic signals.
Collapse
Affiliation(s)
- H Larsson
- Department of Medical Biochemistry and Microbiology, Uppsala University Biomedical Center, Box 575, S-751 23 Uppsala, Sweden
| | | | | | | |
Collapse
|
39
|
Gelkop S, Isakov N. T cell activation stimulates the association of enzymatically active tyrosine-phosphorylated ZAP-70 with the Crk adapter proteins. J Biol Chem 1999; 274:21519-27. [PMID: 10419455 DOI: 10.1074/jbc.274.31.21519] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Engagement of the T cell antigen receptor initiates signal transduction involving tyrosine phosphorylation of multiple effector molecules and the formation of multimolecular complexes at the receptor site. Adapter proteins that possess SH2 and SH3 protein-protein interaction domains are implicated in the assembly of cell activation-induced signaling complexes. We found that Crk adapter proteins undergo activation-induced interaction with the zeta-chain associated protein (ZAP-70) tyrosine kinase in the human T cell line, Jurkat. Incubation of various glutathione S-transferase fusion proteins with a lysate of activated Jurkat cells resulted in selective association of ZAP-70 with Crk, but not Grb2 or Nck, adapter proteins. In addition, tyrosine-phosphorylated ZAP-70 co-immunoprecipitated with Crk from a lysate of activated Jurkat cells, and ZAP-70 association with GST-Crk was observed in a lysate of activated human peripheral blood T cells. Association between the two molecules was mediated by direct physical interaction and involved the Crk-SH2 domain and phosphotyrosyl-containing sequences on ZAP-70. The association required intact Lck, considered to be an upstream regulator of ZAP-70, because it could not take place in activated JCaM1 cells, which express normal levels of ZAP-70 but are devoid of Lck. Finally, glutathione S-transferase-Crk fusion proteins were found to interact predominantly with membrane-residing tyrosine-phosphorylated ZAP-70 that exhibited autophosphorylation activity as well as phosphorylation of an exogenous substrate, CFB3. These findings suggest that Crk adapter proteins play a role in the early activation events of T lymphocytes, apparently, by direct interaction with, and regulation of, the membrane-residing ZAP-70 protein tyrosine kinase.
Collapse
Affiliation(s)
- S Gelkop
- Department of Microbiology and Immunology, Faculty of Health Sciences, Cancer Research Center, Ben Gurion University of the Negev, Beer Sheva 84105, Israel
| | | |
Collapse
|
40
|
Chen XQ, Tan I, Leung T, Lim L. The myotonic dystrophy kinase-related Cdc42-binding kinase is involved in the regulation of neurite outgrowth in PC12 cells. J Biol Chem 1999; 274:19901-5. [PMID: 10391936 DOI: 10.1074/jbc.274.28.19901] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The myotonic dystrophy kinase-related Cdc42-binding kinase (MRCKalpha) has been implicated in the morphological activities of Cdc42 in nonneural cells. Both MRCKalpha and the kinase-related Rho-binding kinase (ROKalpha) are involved in nonmuscle myosin light-chain phosphorylation and associated actin cytoskeleton reorganization. We now show that in PC12 cells, overexpression of the kinase domain of MRCKalpha and ROKalpha resulted in retraction of neurites formed on nerve growth factor (NGF) treatment, as observed with RhoA. However, introduction of kinase-dead MRCKalpha did not result in NGF-independent neurite outgrowth as observed with dominant negative kinase-dead ROKalpha or the Rho inhibitor C3. Neurite outgrowth induced by NGF or kinase-dead ROKalpha was inhibited by dominant negative Cdc42(N17), Rac1(N17), and the Src homology 3 domain of c-Crk, indicating the participation of common downstream components. Neurite outgrowth induced by either agent was blocked by kinase-dead MRCKalpha lacking the p21-binding domain or by a minimal C-terminal regulatory region consisting of the cysteine-rich domain/pleckstrin homology domain plus a region with homology to citron. The latter region alone was an effective blocker of NGF-induced outgrowth. These results suggest that although ROKalpha is involved in neurite retraction promoted by RhoA, the related MRCKalpha is conversely involved in neurite outgrowth promoted by Cdc42 and Rac.
Collapse
Affiliation(s)
- X Q Chen
- Glaxo-IMCB Group, Institute of Molecular and Cell Biology, Singapore 117609, Singapore
| | | | | | | |
Collapse
|
41
|
Buday L. Membrane-targeting of signalling molecules by SH2/SH3 domain-containing adaptor proteins. BIOCHIMICA ET BIOPHYSICA ACTA 1999; 1422:187-204. [PMID: 10393272 DOI: 10.1016/s0304-4157(99)00005-2] [Citation(s) in RCA: 106] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
SH2/SH3 domain-containing adaptor proteins play a critical role in regulating tyrosine kinase signalling pathways. The major function of these adaptors, such as Grb2, Nck, and Crk, is to recruit proline-rich effector molecules to tyrosine-phosphorylated kinases or their substrates. In recent years dozens of novel proteins have emerged that are capable of associating with the SH2 and the SH3 domains of adaptors. In this review, the author attempts to summarise these novel binding partners of Grb2, Nck, and Crk, and to discuss current controversies regarding function and regulation of protein multicomplexes held together by SH2/SH3 adaptor molecules at the plasma membrane.
Collapse
Affiliation(s)
- L Buday
- Department of Medical Chemistry, Semmelweis University Medical School, 9 Puskin Street, 1088, Budapest, Hungary.
| |
Collapse
|
42
|
Meakin SO, MacDonald JI, Gryz EA, Kubu CJ, Verdi JM. The signaling adapter FRS-2 competes with Shc for binding to the nerve growth factor receptor TrkA. A model for discriminating proliferation and differentiation. J Biol Chem 1999; 274:9861-70. [PMID: 10092678 DOI: 10.1074/jbc.274.14.9861] [Citation(s) in RCA: 177] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We have isolated a human cDNA for the signaling adapter molecule FRS-2/suc1-associated neurotrophic factor target and shown that it is tyrosine-phosphorylated in response to nerve growth factor (NGF) stimulation. Importantly, we demonstrate that the phosphotyrosine binding domain of FRS-2 directly binds the Trk receptors at the same phosphotyrosine residue that binds the signaling adapter Shc, suggesting a model in which competitive binding between FRS-2 and Shc regulates differentiation versus proliferation. Consistent with this model, FRS-2 binds Grb-2, Crk, the SH2 domain containing tyrosine phosphatase SH-PTP-2, the cyclin-dependent kinase substrate p13(suc1), and the Src homology 3 (SH3) domain of Src, providing a functional link between TrkA, cell cycle, and multiple NGF signaling effectors. Importantly, overexpression of FRS-2 in cells expressing an NGF nonresponsive TrkA receptor mutant reconstitutes the ability of NGF to stop cell cycle progression and to stimulate neuronal differentiation.
Collapse
Affiliation(s)
- S O Meakin
- Neurodegeneration Research Group, The John P. Robarts Research Institute, London, Ontario N6A 5K8, Canada.
| | | | | | | | | |
Collapse
|
43
|
Lupher ML, Rao N, Lill NL, Andoniou CE, Miyake S, Clark EA, Druker B, Band H. Cbl-mediated negative regulation of the Syk tyrosine kinase. A critical role for Cbl phosphotyrosine-binding domain binding to Syk phosphotyrosine 323. J Biol Chem 1998; 273:35273-81. [PMID: 9857068 DOI: 10.1074/jbc.273.52.35273] [Citation(s) in RCA: 146] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The proto-oncogene product Cbl has emerged as a potential negative regulator of the Syk tyrosine kinase; however, the nature of physical interactions between Cbl and Syk that are critical for this negative regulation remains unclear. Here we show that the phosphotyrosine-binding (PTB) domain within the N-terminal transforming region of Cbl (Cbl-N) binds to phosphorylated Tyr323 in the linker region between the Src homology 2 and kinase domains of Syk, confirming recent results by another laboratory using the yeast two-hybrid approach (Deckert, M., Elly, C., Altman, A., and Liu, Y. C. (1998) J. Biol. Chem. 273, 8867-8874). A PTB domain-inactivating point mutation (G306E), corresponding to a loss-of-function mutation in the Caenorhabditis elegans Cbl homologue SLI-1, severely compromised Cbl-N/Syk binding in vitro and Cbl/Syk association in transfected COS-7 cells. Using heterologous expression in COS-7 cells, we investigated the role of Cbl PTB domain binding to Syk Tyr323 in the negative regulation of Syk. Co-expression of Cbl with Syk in COS-7 cells led to a dose-dependent decrease in the autophosphorylated pool of Syk and in phosphorylation of an in vivo substrate, CD8-zeta. Unexpectedly, these effects were largely due to the loss of Syk protein. Both the decrease in Syk and CD8-zeta phosphorylation and reduction in Syk protein levels were blocked by either G306E mutation in Cbl or by Y323F mutation in Syk. These results demonstrate a critical role for the Cbl PTB domain in the recruitment of Cbl to Syk and in Cbl-mediated negative regulation of Syk.
Collapse
Affiliation(s)
- M L Lupher
- Lymphocyte Biology Section, Division of Rheumatology, Immunology and Allergy, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA
| | | | | | | | | | | | | | | |
Collapse
|
44
|
Ohoka Y, Takai Y. Isolation and characterization of cortactin isoforms and a novel cortactin-binding protein, CBP90. Genes Cells 1998; 3:603-12. [PMID: 9813110 DOI: 10.1046/j.1365-2443.1998.00216.x] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND Cortactin is a major phosphotyrosyl protein in pp60v-src-transformed chicken embryo cells. Cortactin binds to actin filament (F-actin) through a unique region which consists of six tandem 37 amino acid repeats, named cortactin repeats. Furthermore cortactin has one src homology 3 (SH3) domain. RESULTS In this study we have isolated two new isoforms of cortactin from the rat brain using a polymerase chain reaction (PCR) method, and have named the original cortactin as cortactin-A and the newly isolated forms as cortactin-B and -C. Cortactin-A, -B and -C had six, five, and four cortactin repeats, respectively. All the isoforms were able to bind to F-actin, but only cortactin-A demonstrated an F-actin-crosslinking activity. In addition, cortactin-A was able to bind along the side of F-actin. Next, using a blot overlay assay with glutathione S-transferase (GST)-cortactin-A, we identified a cortactin-A-binding protein with an Mr of approximately 90 kDa in rat brain and named it CBP90 (cortactin-binding protein with an Mr of approximately 90 KDa). CBP90 was purified from rat brain and its cDNA was cloned from a rat brain cDNA library. The deduced amino acid sequence of CBP90 had no significant similarity to any other protein, but it had a proline-rich domain at the C-terminal region. CBP90 was able to bind to all the cortactin isoforms. A deletion mutant analysis of cortactin-A and CBP90 revealed that the SH3 domain of cortactin-A was able to bind to the proline-rich region of CBP90. A Western blot analysis with an anti-CBP90 antibody indicated that, among the rat tissues examined, CBP90 was exclusively expressed in brain. Furthermore, its subcellular distribution and developmental expression patterns were similar to those of cortactin. CONCLUSION These results suggest that cortactin interacts with CBP90 and plays a role in regulation of the actin cytoskeleton in brain.
Collapse
Affiliation(s)
- Y Ohoka
- Takai Biotimer Project, ERATO, Japan Science and Technology Corporation, 2-2-10 Murotani, Nishi-ku, Kobe 651-2241, Japan
| | | |
Collapse
|
45
|
Koval AP, Karas M, Zick Y, LeRoith D. Interplay of the proto-oncogene proteins CrkL and CrkII in insulin-like growth factor-I receptor-mediated signal transduction. J Biol Chem 1998; 273:14780-7. [PMID: 9614078 DOI: 10.1074/jbc.273.24.14780] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The closely related proto-oncogene proteins CrkII and CrkL consist of one SH2 and two SH3 domains and share 60% overall homology with the highest identity within their functional domains. In this study we show that CrkL and CrkII may play overlapping but different roles in insulin-like growth factor (IGF)-I receptor-mediated signal transduction. While both proteins are substrates involved in IGF-I receptor signaling, they apparently demonstrate important different properties and different biological responses. Evidence supporting this hypothesis includes (a) the oncogenic potential of CrkL versus the absence of this potential in CrkII overexpressing cell lines, (b) the inhibition of IGF-I-dependent cell cycle progression by overexpression of CrkII, and (c) the differential regulation of the phosphorylation status of selective proteins in CrkII and CrkL overexpressing cell lines. In addition we demonstrate the specific association of CrkL and CrkII with the newly characterized IRS-4 protein, again in a differential manner. Whereas CrkL strongly interacts with IRS-4 via its SH2 and N-terminal SH3 domains, CrkII interacts only via its SH2 domain, possibly explaining the unstable nature of IRS-4-CrkII association. The results obtained allow us to propose a unique mechanism of CrkL and CrkII tyrosine phosphorylation in response to IGF-I stimulation. Thus these highly homologous proteins apparently possess structural features that allow for the differential association of each protein with different effector molecules, thereby activating different signaling pathways and resulting in unique biological roles of these proteins.
Collapse
Affiliation(s)
- A P Koval
- Diabetes Branch, NIDDK, National Institutes of Health, Bethesda, Maryland 20892, USA
| | | | | | | |
Collapse
|
46
|
York RD, Yao H, Dillon T, Ellig CL, Eckert SP, McCleskey EW, Stork PJ. Rap1 mediates sustained MAP kinase activation induced by nerve growth factor. Nature 1998; 392:622-6. [PMID: 9560161 DOI: 10.1038/33451] [Citation(s) in RCA: 698] [Impact Index Per Article: 26.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Activation of mitogen-activated protein (MAP) kinase (also known as extracellular-signal-regulated kinase, or ERK) by growth factors can trigger either cell growth or differentiation. The intracellular signals that couple growth factors to MAP kinase may determine the different effects of growth factors: for example, transient activation of MAP kinase by epidermal growth factor stimulates proliferation of PC12 cells, whereas they differentiate in response to nerve growth factor, which acts partly by inducing a sustained activation of MAP kinase. Here we show that activation of MAP kinase by nerve growth factor involves two distinct pathways: the initial activation of MAP kinase requires the small G protein Ras, but its activation is sustained by the small G protein Rap1. Rap1 is activated by CRK adaptor proteins and the guanine-nucleotide-exchange factor C3G, and forms a stable complex with B-Raf, an activator of MAP kinase. Rap1 is required for at least two indices of neuronal differentiation by nerve growth factor: electrical excitability and the induction of neuron-specific genes. We propose that the activation of Rap1 by C3G represents a common mechanism to induce sustained activation of the MAP kinase cascade in cells that express B-Raf.
Collapse
Affiliation(s)
- R D York
- The Vollum Institute for Advanced Biomedical Research, Oregon Health Sciences University, Portland 97201, USA
| | | | | | | | | | | | | |
Collapse
|
47
|
Ota S, Kizaka-Kondoh S, Hashimoto Y, Nishihara H, Nagashima K, Kurata T, Okayama H, Matsuda M. Constitutive association of EGF receptor with the CrkII-23 mutant that inhibits transformation of NRK cells by EGF and TGF-beta. Cell Signal 1998; 10:283-90. [PMID: 9617486 DOI: 10.1016/s0898-6568(97)00130-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Crk belongs to the adapter proteins that participate in many signalling pathways from cell surface receptors. We have characterised the CrkII-23 mutant that inhibits the transformation of NRK cells induced by epidermal growth factor (EGF) and transforming growth factor (TGF)-beta. To study the biochemical difference, cDNAs of the wild-type CrkII and the CrkII-23 mutant were introduced stably into NIH 3T3 cells expressing EGF receptor (EGFR). Both CrkII and CrkII-23 were phosphorylated on tyrosine upon EGF simulation with similar time course and dose dependency. Whereas the wild-type CrkII bound to EGFR only after EGF stimulation, CrkII-23 bound to EGFR from before stimulation. Mutation in the Src homology (SH) 2 or amino-terminal SH3 domain did not abolish the binding of CrkII-23 to EGFR in the quiescent cells, suggesting that the binding is mediated by a novel mechanism. These CrkII-23-derived mutants, however, did not suppress transformation of NRK cells by EGF and TGF-beta. Hence, both the SH2 and amino-terminal SH3 domains are required to inhibit transformation of NRK cells. These results suggest that persistent signalling from CrkII-23 bound to EGFR suppresses transformation by EGF and TGF-beta in NRK23 cells.
Collapse
Affiliation(s)
- S Ota
- Department of Pathology, National Institute of Infectious Diseases, Tokyo, Japan
| | | | | | | | | | | | | | | |
Collapse
|
48
|
Itoh S, Nukuzuma S, Nukuzuma C, Tanaka S, Nagashima K. Involvement of cell membrane factors in JC virus infection. Neuropathology 1998. [DOI: 10.1111/j.1440-1789.1998.tb00080.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
49
|
Klemke RL, Leng J, Molander R, Brooks PC, Vuori K, Cheresh DA. CAS/Crk coupling serves as a "molecular switch" for induction of cell migration. J Cell Biol 1998; 140:961-72. [PMID: 9472046 PMCID: PMC2141747 DOI: 10.1083/jcb.140.4.961] [Citation(s) in RCA: 562] [Impact Index Per Article: 21.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Carcinoma cells selected for their ability to migrate in vitro showed enhanced invasive properties in vivo. Associated with this induction of migration was the anchorage-dependent phosphorylation of p130CAS (Crk-associated substrate), leading to its coupling to the adaptor protein c-CrkII (Crk). In fact, expression of CAS or its adaptor protein partner Crk was sufficient to promote cell migration, and this depended on CAS tyrosine phosphorylation facilitating an SH2-mediated complex with Crk. Cytokine-stimulated cell migration was blocked by CAS lacking the Crk binding site or Crk containing a mutant SH2 domain. This migration response was characterized by CAS/Crk localization to membrane ruffles and blocked by the dominant-negative GTPase, Rac, but not Ras. Thus, CAS/Crk assembly serves as a "molecular switch" for the induction of cell migration and appears to contribute to the invasive property of tumors.
Collapse
Affiliation(s)
- R L Klemke
- Department of Immunology, The Scripps Research Institute, La Jolla, California 92037, USA.
| | | | | | | | | | | |
Collapse
|
50
|
Hata K, Ito T, Takeshige K, Sumimoto H. Anionic amphiphile-independent activation of the phagocyte NADPH oxidase in a cell-free system by p47phox and p67phox, both in C terminally truncated forms. Implication for regulatory Src homology 3 domain-mediated interactions. J Biol Chem 1998; 273:4232-6. [PMID: 9461621 DOI: 10.1074/jbc.273.7.4232] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Anionic amphiphiles, such as arachidonate, activate the superoxide-producing phagocyte NADPH oxidase in a cell-free system with human neutrophil membrane, which contains cytochrome b558 comprising gp91(phox) and p22(phox), and three cytosolic proteins: p47(phox) and p67(phox), each harboring two SH3 domains, and the small GTPase Rac. Here we show that, even without the amphiphiles, the oxidase is activated in vitro by a C terminally truncated p47(phox), retaining the N-terminal and the two SH3 domains, and the N terminus of p67(phox). When either truncated p47(phox) or p67(phox) is replaced by the respective full-length one, the activation absolutely requires the amphiphiles. The results indicate that both p47(phox) and p67(phox) are the primary targets of the amphiphiles, and that their C-terminal regions play negative regulatory roles. We also find that the truncated p47(phox), but not the full-length one, can bind to p22(phox), a binding required for the oxidase activation. The N-terminal SH3 domain of p47(phox) is responsible for the binding not only to p22(phox), but also to the p47(phox) C terminus. Thus the SH3 domain is accessible in the active p47(phox), but is normally masked in the full-length one probably via intramolecularly interacting with the C terminus. The present findings support our previous proposal of regulatory SH3 domain-mediated interactions.
Collapse
Affiliation(s)
- K Hata
- Department of Biochemistry, Kyushu University School of Medicine, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-82, Japan
| | | | | | | |
Collapse
|