Michiyuki Matsuda

Rho family G proteins, including Rac and Cdc42, regulate a variety of cellular functions such as morphology, motility, and gene expression. We developed fluorescent resonance energy transfer-based probes which monitored the local balance between the activities of guanine nucleotide exchange factors and GTPase-activating proteins for Rac1 and Cdc42 at the membrane. These probes, named Raichu-Rac and Raichu-Cdc42, consisted of a Cdc42- and Rac-binding domain of Pak, Rac1 or Cdc42, a pair of green

Although the oncogene product of CT10 virus, P47gag-crk, does not itself phosphorylate proteins at tyrosine residues, it elevates phosphotyrosine in transformed cells. The P47gag-crk oncoprotein contains SH2 and SH3 domains, which are conserved in several proteins involved in signal transduction, including nonreceptor tyrosine kinases. P47gag-crk bound in vitro to phosphotyrosine-containing proteins from crk-transformed cells and from cells transformed by oncogenic tyrosine kinases. The associat

Two distinct human CRK cDNAs, designated CRK-I and CRK-II, were isolated from human embryonic lung cells by polymerase chain reaction and by screening of a human placenta cDNA library, respectively. CRK-I differed from CRK-II in that it lacked a 170-nucleotide sequence, suggesting that CRK-I and CRK-II were the products of alternative splicing. The amino acid sequences deduced from these two cDNAs differed in the carboxyl termini and contained one SH2 and either one or two SH3 domains. RNAse pro

A major function of Rho-family GTPases is to regulate the organization of the actin cytoskeleton; filopodia, lamellipodia, and stress fiber are regarded as typical phenotypes of the activated Cdc42, Rac, and Rho, respectively. Using probes based on fluorescent resonance energy transfer, we report on the spatiotemporal regulation of Rac1 and Cdc42 at lamellipodia and membrane ruffles. In epidermal growth factor (EGF)-stimulated Cos1 and A431 cells, both Rac1 and Cdc42 were activated diffusely at

It has been reported that growth factors activate Ras through a complex of an adaptor type SH2-containing molecule, Grb2, and a Ras guanine nucleotide-releasing protein (GNRP), mSos. We report on the involvement of another adaptor molecule, CRK, in the activation of Ras. Overexpression of wild-type CRK proteins CRK-I and CRK-II enhanced the nerve growth factor (NGF)-induced activation of Ras in PC12 cells, although the basal level of GTP-bound active Ras was not altered. In contrast, mutants wit

The oncogene product of the avian sarcoma virus CT10, P47gag-crk, contains the SH2, SH2', and SH3 domains and binds proteins in a phosphotyrosine (ptyr)-dependent manner. In this study, we have determined the region of P47gag-crk essential for binding to ptyr-containing proteins. Mutant P47gag-crk proteins expressed in Escherichia coli that have the intact SH2 and SH2' regions retained the capacity to bind ptyr-containing proteins obtained from cells transformed by crk and src. The deletion of S

Rho family GTPases play pivotal roles in cytokinesis. By using probes based on the principle of fluorescence resonance energy transfer (FRET), we have shown that in HeLa cells RhoA activity increases with the progression of cytokinesis. Here we show that in Rat1A cells RhoA activity remained suppressed during most of the cytokinesis. Consistent with this observation, the expression of C3 toxin inhibited cytokinesis in HeLa cells but not in Rat1A cells. Furthermore, the expression of a dominant n