Integrins engage in bidirectional signaling. Fibrinogen binding to integrins is regulated by inside-out signals initiated by agonist receptors, a process often called “integrin activation.” In turn, ligandbound integrins transduce outside-in signals to regulate cellular responses, among them cytoskeletal reorganization. In platelets, integrin aIIbb3 bidirectional signaling is required for effic...

A large superfamily (> 50 members) of monomeric GTPbinding proteins structurally related to the ras oncogene proteins has been described in the past few years (Bourne et al., 1991; Grand and Owen, 1991; Hall, 1990; Valencia et al., 1991). These proteins have been implicated in the regulation of a diverse array of cellular processes, utilizing their ability to bind and hydrolyse GTP as a means t...

The three mammalian ras proteins associate specifically with the plasma membrane and this is essential for their biological activity. Two signals encoded within the extreme COOH terminus of the proteins specify this cellular localization; a CAAX box in combination with either a polybasic domain (p21K-~B) or a palmitoylation site (p21 m-~ and p21N-~). All members of the ras-like and rho-like sub...

The rho proteins, p21 ~ , are ubiquitously expressed guanine nucleotide binding proteins with ,'o30% amino acid homology to p21'% but their biochemical function is unknown. We show here that microinjection of constitutively activated recombinant rho protein (Vall4rho) into subconfluent cells induces dramatic changes in cell morphology: 15-30 min after injection cells adopt a distinct and novel ...