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Results for “src Homology Domains”

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PubMed1996

Src homology domains of v-Src stabilize an active conformation of the tyrosine kinase catalytic domain.

To examine the interactions between Src homology domains and the tyrosine kinase catalytic domain of v-Src, various combinations of domains have been expressed in bacteria as fusion proteins. Constructs containing the isolated catalytic domain, SH2 + catalytic domain, and SH3 + SH2 + catalytic domains were active in autophosphorylation assays. For the catalytic domain of v-Src, but not for v-Abl, addition of exogenous Src SH3-SH2 domains stimulated the autophosphorylation activity. In contrast to results for autophosphorylation, constructs containing Src homology domains were more active towards a synthetic peptide substrate than the isolated catalytic domain. The ability of the SH2 and SH3 domains of v-Src to stabilize an active enzyme conformation was also confirmed by refolding after denaturation in guanidinium hydrochloride. Collectively the data suggest that, in addition to their roles in intermolecular protein-protein interactions, the Src homology regions of v-Src exert a positive influence on tyrosine kinase function, potentially by maintaining an active conformation of the catalytic domain.

Adenosine Triphosphate↗

PubMed1996

Identification of regions of the Wiskott-Aldrich syndrome protein responsible for association with selected Src homology 3 domains.

Src homology 3 (SH3) domains have been shown to mediate selected interactions between signaling molecules and are essential for the activation of a number of receptor-driven pathways. The Wiskott-Aldrich syndrome protein was identified as a protein that associated selectively with the SH3 domains derived from c-Src, p85alpha, phospholipase Cgamma1, and c-Fgr. Significantly reduced association was detected to the N-terminal SH3 domain and the tandem SH3 domains of p47(phox), and no binding was detected to the SH3 domain of n-Src, the C-terminal SH3 domain of p47(phox), or either of the SH3 domains of p67(phox). Three peptides corresponding to potential Wiskott-Aldrich syndrome protein SH3 domain binding motifs were found to inhibit its association with c-Src, Fgr, and phospholipase Cgamma1 SH3 domains, but not the p85alpha SH3 domain. These peptides have the sequences MRRQEPLPPPPPPSRG, TGRSGPLPPPPPGA, and KGRSGPLPPVPLGI and show homology with other SH3 domain binding motifs. It is possible that the intracellular association of Wiskott-Aldrich syndrome protein with other signaling proteins is mediated by its SH3 domain-binding regions, and this may play a role in its putative function as a regulatory molecule in immune cells.

Amino Acid Sequence↗

PubMed1992

High-efficiency expression/cloning of epidermal growth factor-receptor-binding proteins with Src homology 2 domains.

Src homology 2 domains bind to tyrosine-phosphorylated growth factor receptors and are found in proteins that serve as substrates for tyrosine kinases, such as phospholipase C-gamma 1 and ras GTPase-activating protein. We have previously described the cloning of phosphatidylinositol 3'-kinase-associated p85 from expression libraries with the tyrosine-phosphorylated epidermal growth factor receptor as a probe. We have now modified this technique by using T7 polymerase-based expression libraries, which significantly improves sensitivity of the method. In one screening of such a library, we identified five different murine Src homology 2 domain-containing proteins, which we call GRBs (growth factor receptor-bound proteins). Two of these proteins represented the tyrosine kinase fyn and the mouse homologue of phospholipase C-gamma 1, whereas two genes encoded proteins similar to v-crk and NCK. We also isolated the gene for GRB-7, which encodes a protein of 535 amino acids. In addition to a Src homology 2 domain, GRB-7 also has a region of similarity to the noncatalytic domain of ras GTPase-activating protein and is highly expressed in liver and kidney. Use of this expression/cloning system should increase our ability to identify downstream modulators of growth factor action.

Amino Acid Sequence↗

PubMed1995

Cooperation of Src homology domains in the regulated binding of phosphatidylinositol 3-kinase. A role for the Src homology 2 domain.

Fibroblasts transformed by the v-Src oncoprotein exhibit elevated activity of the enzyme phosphatidylinositol 3'-kinase (PI 3-kinase), which binds to, and is activated by, a wide range of receptor tyrosine kinases as well as v-Src and transforming polyoma middle T/c-Src complexes. Here we consider the role of the v-Src homology (SH) domains, SH3 and SH2, and the tyrosine kinase catalytic domain, in the stimulation of v-Src-associated PI 3-kinase activity in response to rapid activation of the oncoprotein. As shown by others, we find that the v-Src SH3 domain tightly binds the PI 3-kinase p85 regulatory subunit in normal growing chicken embryo fibroblasts. However, we also find that in transformed cells there is additional efficient binding of PI 3-kinase to the v-Src SH2 domain in a catalytically active form. Furthermore, the binding of p85 to the SH2 domain, which is almost undetectable in quiescent cells, is rapidly stimulated upon activation of temperature-sensitive v-Src and consequent cell cycle entry, demonstrating that binding is a target for regulation. We also show that v-Src-associated PI 3-kinase differs considerably from PDGF receptor-associated enzyme by a different mode of binding, a lack of substantial allosteric activation, and a dependence on the tyrosine kinase activity of v-Src. The rapidly induced binding and activation of PI 3-kinase thus provides sensitive regulation of recruitment of PI 3-kinase to its substrates and into other signaling complexes at the cell membrane, which involves all the Src homology domains.

Amino Acid Sequence↗

PubMed1997

Heteronuclear NMR studies of the combined Src homology domains 2 and 3 of pp60 c-Src: effects of phosphopeptide binding.

The results of heteronuclear NMR studies on the combined Src homology domains 2 and 3 (SH3-SH2) of pp60 c-Src are presented. Resonance assignments were obtained using heteronuclear triple-resonance experiments in conjunction with 15N-separated nuclear Overhauser effect spectroscopy (NOESY) data. A modified three-dimensional 13CO-15N-1H spectral correlation experiment [(HACA)CO(CA)-NH] with improved sensitivity is presented that provided additional sequential information and resolved several ambiguities. Chemical shifts and sequential- and medium-range NOE cross peaks indicate that the structures of both the SH3 and SH2 portions of the polypeptide are very similar to those of the isolated SH3 and SH2 domains. Binding of a high-affinity phosphopeptide, EPQpYEEIPIYL, induces large chemical shift changes at several locations in the SH2 domain. Comparison with known results for peptide binding to SH2 domains shows that the residues displaying the largest effects are all involved in peptide binding or undergo significant conformational changes upon binding. However, subtle changes of both 1H and 15N chemical shifts are observed for residues within the SH3 domain and the connecting linker region, indicating possible cross-domain communication.

Amino Acid Sequence↗

PubMed1997

The role of the Src homology domains in morphological transformation by v-src.

The Src homology (SH2 and SH3) domains of v-Src are required for transformation of Rat-2 cells and for wild-type (morphr) transformation of chicken embryo fibroblasts (CEFs). We report herein that the N-terminal domains of v-Src, when expressed in trans, cannot complement the transformation defect of a deletion mutant lacking the "unique," SH3, and SH2 regions. However, the same regions of Src can promote transformation when translocated to the C terminus of v-Src, although the transformation of CEFs is somewhat slower. We conclude that the SH3 and SH2 domains must be present in cis to the catalytic domain to promote transformation but that transformation is not dependent on the precise intramolecular location of these domains. In CEFSs and in Rat-2 cells, the expression of wild-type v-Src results in tyrosine phosphorylation of proteins that bind to the v-Src SH3 and SH2 domains in vitro; mutations in the SH2 or SH3 and SH2 domains prevent the phosphorylation of these proteins. These findings are most consistent with models in which the SH3 and SH2 domains of v-Src directly or indirectly target the catalytic domain to substrates involved in transformation. However, the N-terminal domains of v-Src can promote tyrosine phosphorylation of certain proteins, in particular p130Cas, even when expressed in the absence of the catalytic domain, indicating that the N-terminal domains of v-Src have effects that are independent of the catalytic domain.

Animals↗

PubMed1996

Differences in binding of PI 3-kinase to the src-homology domains 2 and 3 of p56 lck and p59 fyn tyrosine kinases.

Two T cell-specific src-family tyrosine kinases, p56 lck (lck) and p59 fyn (fyn), are implicated in regulating PI 3-kinase activity in response to interleukin-2 (IL-2), a cytokine that induces T cell proliferation. The src- homology domains 3 (SH3) of src-family kinases can directly interact with the PI 3-kinase regulatory subunit p85 and this may be a mechanism to regulate PI 3-kinase activity. In order to understand the mode of PI 3-kinase activation by the IL-2 receptor, we examined the association of PI 3-kinase to SH2 and SH3 domains of lck and fyn in IL-2-dependent kit 225 cells. The fyn SH3 domain bound more PI 3-kinase and its p85 subunit than the lck SH3 domain, while the lck SH2 domain bound more PI 3-kinase than the fyn SH2 domain. None of these interactions were regulated by IL-2. Low binding of PI 3-kinase to the lck SH3 domain was not observed in IL-2-independent Jurkat T cells. Thus, SH3 and SH2 domains of lck and fyn bound different amounts of PI 3-kinase, a feature that was dependent on a T cell type, but was not influenced by IL-2.

Amino Acid Sequence↗

PubMed1996

Src-homology domain 2 is responsible for transcriptional suppression induced by expression of Lck.

Overexpression of Lck was shown, by our previous study, to suppress gene transcription from various viral and cellular promoters. The suppression of transcription from human T-cell leukemia virus promoter by Lck was independent of the presence of the enhancer core sequences within the long terminal repeat. The suppression of transcription was observed with Lck mutants that had either diminished or enhanced tyrosine-kinase activity. A mutant lacking the myristylation site also suppressed transcription. From the analysis with various deletion mutants of Lck, it was suggested that Src-homology domain 2 (SH2) is both necessary and sufficient for the suppression of transcription. A similar effect was also observed with the SH2 domain of the v-src gene. Thus, overexpression of Lck could suppress gene expression through a unique function of the SH2 domain.

Amino Acid Sequence↗

PubMed1996

PLC gamma 1 Src homology domain induces mitogenesis in quiescent NIH 3T3 fibroblasts.

Previously, we demonstrated that microinjection of phosphoinositide-specific phospholipase C gamma 1 (PLC gamma 1) and lipase-defective mutants of PLC gamma 1 induced G(0) growth arrested NIH 3T3 fibroblasts to enter S phase of the cell cycle. These experiments suggested that regions other than the catalytic domain of PLC gamma 1 may be responsible for inducing mitogenesis. To test other regions of PLC gamma 1 for DNA synthesis inducing activity, cDNA fragments encoding Src homology (SH) and pleckstrin homology (PH) domains were subcloned into the bacterial expression plasmid pGEX-2TK, and the GST fusion proteins were purified. The complete PLC gamma l SH domain peptide was found to induce DNA synthesis after microinjection into growth arrested fibroblasts. Peptides containing a single SH3 domain or two SH2 domains induced a partial response that was restored to full activity if they were co-injected. The PH domain peptide did not induce DNA synthesis. Thus, both SH3 and SH2 activity combine to give maximum DNA synthesis induction, demonstrating that non-catalytic structural domains of PLC gamma 1 have pronounced effects on mitogenic signaling pathways.

3T3 Cells↗

PubMed1998

The Src homology domain 3 (SH3) of a yeast type I myosin, Myo5p, binds to verprolin and is required for targeting to sites of actin polarization.

The budding yeast contains two type I myosins, Myo3p and Myo5p, with redundant functions. Deletion of both myosins results in growth defects, loss of actin polarity and polarized cell surface growth, and accumulation of intracellular membranes. Expression of myc-tagged Myo5p in myo3Delta myo5Delta cells fully restores wild-type characteristics. Myo5p is localized as punctate, cortical structures enriched at sites of polarized cell growth. We find that latrunculin-A-induced depolymerization of F-actin results in loss of Myo5p patches. Moreover, incubation of yeast cells at 37 degrees C results in transient depolarization of both Myo5p patches and the actin cytoskeleton. Mutant Myo5 proteins with deletions in nonmotor domains were expressed in myo3Delta myo5Delta cells and the resulting strains were analyzed for Myo5p function. Deletion of the tail homology 2 (TH2) domain, previously implicated in ATP-insensitive actin binding, has no detectable effect on Myo5p function. In contrast, myo3Delta myo5Delta cells expressing mutant Myo5 proteins with deletions of the src homology domain 3 (SH3) or both TH2 and SH3 domains display defects including Myo5p patch depolarization, actin disorganization, and phenotypes associated with actin dysfunction. These findings support a role for the SH3 domain in Myo5p localization and function in budding yeast. The proline-rich protein verprolin (Vrp1p) binds to the SH3 domain of Myo3p or Myo5p in two-hybrid tests, coimmunoprecipitates with Myo5p, and colocalizes with Myo5p. Immunolocalization of the myc-tagged SH3 domain of Myo5p reveals diffuse cytoplasmic staining. Thus, the SH3 domain of Myo5p contributes to but is not sufficient for localization of Myo5p either to patches or to sites of polarized cell growth. Consistent with this, Myo5p patches assemble but do not localize to sites of polarized cell surface growth in a VRP1 deletion mutant. Our studies support a multistep model for Myo5p targeting in yeast. The first step, assembly of Myo5p patches, is dependent upon F-actin, and the second step, polarization of actin patches, requiresVrp1p and the SH3 domain of Myo5p.

Actins↗

PubMed1995

Competitive binding assay of src homology domain 3 interactions between 5-lipoxygenase and growth factor receptor binding protein 2.

c-src homology 3 domains (SH3) modulate the formation of a number of protein complexes that are important in cell signaling and cytoskeletal organization. The SH3 domain is recognized by short conserved proline-rich motifs which adopt left-handed polyproline helices on binding. In order to examine molecular determinants of the proline motif:SH3 interaction, an enzyme-linked immunosorbent assay was developed to observe binding of 5-lipoxygenase to SH3 domains of growth factor receptor binding protein 2 (Grb2). The assay makes use of glutathione S-transferase fusion proteins of Grb2 and fragments of Grb2 immobilized onto wells of standard 96-well microtiter plates. Equilibrium binding is monitored colorimetrically and the measured absorbance is proportional to 5-LO concentration. The interactions is specific for the Grb2 portion of the fusion proteins, and 5-LO binds preferentially to Grb2 fragments containing an SH3 domain. Competitive binding assays with a synthetic peptide which mimicked the proline-rich region of 5-LO yielded results that are consistent with previous estimates. Binding was examined in the presence of a number of peptides containing the consensus sequence -PXXP-, in the presence of enzyme activity mediators and in the presence of plant lipoxygenases that lack the proline-rich binding motif. Results suggest that the specificity of the Grb2:5-LO interaction is high.

Adaptor Proteins, Signal Transducing↗

PubMed1994

Deletion within the Src homology domain 3 of Bruton's tyrosine kinase resulting in X-linked agammaglobulinemia (XLA).

The gene responsible for X-linked agammaglobulinemia (XLA) has been recently identified to code for a cytoplasmic tyrosine kinase (Bruton's agammaglobulinemia tyrosine kinase, BTK), required for normal B cell development. BTK, like many other cytoplasmic tyrosine kinases, contains Src homology domains (SH2 and SH3), and catalytic kinase domain. SH3 domains are important for the targeting of signaling molecules to specific subcellular locations. We have identified a family with XLA whose affected members have a point mutation (g-->a) at the 5' splice site of intron 8, resulting in the skipping of coding exon 8 and loss of 21 amino acids forming the COOH-terminal portion of the BTK SH3 domain. The study of three generations within this kinship, using restriction fragment length polymorphism and DNA analysis, allowed identification of the mutant X chromosome responsible for XLA and the carrier status in this family. BTK mRNA was present in normal amounts in Epstein-Barr virus-induced B lymphoblastoid cell lines established from affected family members. Although the SH3 deletion did not alter BTK protein stability and kinase activity of the truncated BTK protein was normal, the affected patients nevertheless have a severe B cell defect characteristic for XLA. The mutant protein was modeled using the normal BTK SH3 domain. The deletion results in loss of two COOH-terminal beta strands containing several residues critical for the formation of the putative SH3 ligand-binding pocket. We predict that, as a result, one or more crucial SH3 binding proteins fail to interact with BTK, interrupting the cytoplasmic signal transduction process required for B cell differentiation.

Adult↗

PubMed1991

Nerve growth factor binds to the 140 kd trk proto-oncogene product and stimulates its association with the src homology domain of phospholipase C gamma 1.

The cellular actions of nerve growth factor (NGF) involve regulation of protein phosphorylation. In PC-12 pheochromocytoma cells, exposure of [125I]NGF followed by crosslinking indicates that the ligand binds to two discreet receptors, the previously described 75 kd protein, as well as the trk proto-oncogene product pp140c-trk. Competition experiments reveal that of the two, pp 140c-trk binds to NGF with higher affinity. Following exposure to NGF, pp140c-trk undergoes a rapid autophosphorylation on tyrosine residues, and concomitantly phosphorylates and associates with phospholipase C gamma 1 (PLC gamma 1), through interaction with its src homology domains. The binding of NGF to pp140c-trk with high affinity, the NGF-dependent homology domains. The binding of NGF to pp140c-trk with high affinity, the NGF-dependent activation of its tyrosine kinase activity and the specific association with the effector molecule, PLC gamma 1, suggests that this is the biologically relevant signaling receptor for NGF.

Adrenal Gland Neoplasms↗

PubMed1991

Phospholipase C-gamma 1 directly associates with the p70 trk oncogene product through its src homology domains.

Tyrosine phosphorylation of proteins was examined in NIH3T3 cells transformed by an oncogenic form of the trk protein. Proteins of 148, 140, 70, and 55 kDa were phosphorylated on tyrosine residues in trk-transformed cells but not control NIH3T3 cells. The 70-kDa protein may represent the trk oncogene protein itself which was shown to be tyrosine-phosphorylated in vivo using trk-specific antiserum. Phospholipase C-gamma 1 (PLC-gamma 1) was also found to be constitutively tyrosine-phosphorylated in trk-transformed cells and the trk protein co-immunoprecipitated with PLC-gamma. The GTPase-activating protein of ras (GAP) and the 62-kDa GAP-associated protein were tyrosine-phosphorylated in trk-transformed cells, and a lesser amount of trk co-immunoprecipitated with GAP relative to with PLC-gamma. The trk oncogene product bound specifically to a bacterially expressed fusion protein containing the src homology domains of PLC-gamma. The data suggest a significant role for PLC-gamma in intracellular signaling by the trk oncogene.

Blotting, Western↗

PubMed1995

An alternative role for the src-homology-domain-containing phosphotyrosine phosphatase (SH-PTP2) in regulating epidermal-growth-factor-dependent cell growth.

The association of the src homology 2 (SH2) domain-containing tyrosine phosphatase (SH-PTP2) with the activated epidermal growth factor (EGF) and platelet-derived growth factor receptors, as well as the insulin receptor substrate 1 and growth-factor-receptor-bound protein 2 and its intrinsic tyrosine phosphatase activity suggests an important role for this phosphatase in signal transduction. Previous studies have shown a positive role for SH-PTP2 in growth-factor-mediated cell signaling. We show here that SH-PTP2 can also function to negatively regulate EGF-mediated signal transduction in the human glioma cell line SNB19. We demonstrate this by showing that, in SNB19 cells, which lack the ability to proliferate in response to EGF but retain the ability to bind EGF and also activate the EGF receptor as well as allow for the association of SH-PTP2 with the phosphorylated receptor, stable overexpression of an interfering SH-PTP2 mutant can restore the ability of these cells to proliferate in response to EGF.

Amino Acid Sequence↗

PubMed1996

Thrombin stimulates association of src homology domain containing adaptor protein Nck with pp125FAK.

Thrombin stimulates mitogenesis and tyrosine phosphorylation of several proteins in glomerular mesangial cells [T. Force, J. M. Kyriakis, J. Avruch, and J. V. Bonventre, J. Biol. Chem. 266: 6650-6656, 1991; and G. Grandaliano, G. Ghosh Choudhury, P. Biswas, and H. E. Abboud, Am. J. Physiol. 267 (Renal Fluid Electrolyte Physiol. 36: F528-F536, 1994]. However, none of the tyrosine phosphorylated proteins have been identified. Here we show that thrombin stimulates phosphorylation of four major proteins of molecular masses 170, 125, 97, and 47 kDa in antiphosphotyrosine immunoprecipitates in vitro. Immunoblot analysis of antiphosphotyrosine immunoprecipitates from lysates of thrombin-treated cells with anti-Nck antibody revealed the presence of this src homology domain-containing adaptor molecule in the tyrosine-phosphorylated protein fraction. In addition, in thrombin-treated cells, direct immunoblotting of Nck immunoprecipitates with antiphosphotyrosine antibody showed no tyrosine phosphorylation of Nck. In these immunoprecipitates, we detected a 125-kDa tyrosine-phosphorylated protein. We identified this protein as pp125FAK (FAK, focal adhesion kinase) after analyzing Nck immunoprecipitates by anti-FAK immunoblotting. Treatment of mesangial cells with thrombin resulted in stimulation of the tyrosine kinase activity of pp125FAK in vitro. We conclude that activation of the cytoplasmic protein tyrosine kinase pp125FAK by thrombin stimulates its association with the src homology domain-containing adaptor protein Nck. This indicates that Nck is a direct target for FAK in the thrombin-induced signal transduction pathway.

Adaptor Proteins, Signal Transducing↗

PubMed1992

Nerve growth factor stimulates the tyrosine phosphorylation of a 38-kDa protein that specifically associates with the src homology domain of phospholipase C-gamma 1.

The cellular actions of nerve growth factor (NGF) involve changes in protein phosphorylation, initiated by the binding and subsequent activation of its tyrosine kinase receptor, the trk protooncogene (pp140c-trk). Upon exposure to NGF, a 38-kDa tyrosine-phosphorylated protein (pp38) is identified in both PC-12 pheochromocytoma cells and NIH3T3 cells transfected with the full-length human pp140c-trk cDNA (3T3-c-trk) that is specifically coimmunoprecipitated with pp140c-trk or phosphatidylinositol-phospholipase C (PLC)-gamma 1. In both PC-12 and 3T3-c-trk cells, NGF rapidly stimulates the association of pp140c-trk and pp38 with a fusion protein containing the src homology (SH) domains of PLC gamma 1. This phosphorylation and subsequent association are specific for NGF, since epidermal growth factor, platelet-derived growth factor, and insulin do not stimulate the tyrosine phosphorylation of these proteins or their association with the PLC gamma 1 SH domains, although the receptors for these growth factors do undergo tyrosine phosphorylation and association with the PLC-gamma 1 fusion protein under these conditions. Furthermore, the NGF-dependent pp38-SH binding is specific for the SH2 domains of PLC-gamma 1, since the phosphoprotein does not bind to fusion proteins containing SH domains of ras GTPase-activating protein or the p85 subunit of phosphatidylinositol 3 kinase. Both amino- and carboxyl-terminal SH2 domains of PLC-gamma 1 are necessary for the association of pp38 with PLC-gamma 1, although each SH2 domain is sufficient for the association of pp140c-trk with PLC-gamma 1. In both PC-12 and 3T3-c-trk cells, the phosphorylation and association of pp38 with PLC gamma 1 is rapid, occurring maximally at 1 min and declining thereafter. Moreover, this effect of NGF is dose-dependent over a physiological concentration of the growth factor. The specificity and rapidity of pp38 phosphorylation and its association with PLC-gamma 1 suggest that it may be an important component in signal transduction for NGF.

3T3 Cells↗

PubMed1998

Src homology domains of phospholipase C gamma1 inhibit nerve growth factor-induced differentiation of PC12 cells.

Phospholipase C gamma1 (PLC-gamma1) is phosphorylated on treatment of cells with nerve growth factor (NGF). To assess the role of PLC-gamma1 in mediating the neuronal differentiation induced by NGF treatment, we established PC12 cells that overexpress whole PLC-gamma (PLC-gamma1PC12), the SH2-SH2-SH3 domain (PLC-gamma1SH223PC12), SH2-SH2-deleted mutants (PLC-gamma1deltaSH22PC12), and SH3-deleted mutants (PLC-gamma1deltaSH3PC12). Overexpressed whole PLC-gamma1 or the SH2-SH2-SH3 domain of PLC-gamma1 stimulated cell growth and inhibited NGF-induced neurite outgrowth of PC12 cells. However, cells expressing PLC-gamma1 lacking the SH2-SH2 domain or the SH3 domain had no effect on NGF-induced neuronal differentiation. Overexpression of intact PLC-gamma1 resulted in a threefold increase in total inositol phosphate accumulation on treatment with NGF. However, overexpression of the SH2-SH2-SH3 domain of PLC-gamma1 did not alter total inositol phosphate accumulation. To investigate whether the SH2-SH2-SH3 domain of PLC-gamma1 can mediate the NGF-induced signal, tyrosine phosphorylation of the SH2-SH2-SH3 domain of PLC-gamma1 on NGF treatment was examined. The SH2-SH2-SH3 domain of PLC-gamma1 as well as intact PLC-gamma1 could be tyrosine-phosphorylated on NGF treatment. These results indicate that the overexpressed SH2-SH2-SH3 domain of PLC-gamma1 can block the differentiation of PC12 cells induced by NGF and that the inhibition appears not to be related to the lipase activity of PLC-gamma1 but to the SH2-SH2-SH3 domain of PLC-gamma1.

Animals↗