Structure and function of Cas-L, a 105-kD Crk-associated substrate-related protein that is involved in beta 1 integrin-mediated signaling in lymphocytes.

Abstract

SummaryI.ntegrin/hgand binding evokes tyrosine phosphorylation of various proteins. We reported previously that a 105 kD protein (ppl05) was tyrosine phosphorylated by the engagement of [31 integrins in T lymphocytes. We show here that ppl05 is a novel p130Cas (Crk-associated substrate)-related protein. Deduced amino acid sequence revealed that ppl05 contains conserved motifs with p130Cas, and both ppl05 and p130Cas bind to focal adhesion kinase (pp125FAK) and Crk. However, ppl05 has a clearly distinct structure from p130Cas, and ppl05 is preferentially expressed in lymphocytes, whereas p130Cas is expressed in adherent cells. With these findings, we designate ppl05 as Cas-L, lymphocyte-type Cas. Furthermore, we demonstrate that integrin/hgand binding results in the recruitment of Crk, Nck, and SHPTP2 to ppl05. These findings further define the roles of ppl05/Cas-L and pp125FAK in the integrin-mediated signaling pathways. ever, a 105-kD tyrosine-phosphorylated protein (ppl05) has not been identified.ppl05 is a protein that we first identified in T lymphoblastoid H9 cells as well as peripheral T cells (11). ppl05 is a 105-kD protein that is tyrosine phosphorylated by the engagement of 0L4131 integrin. Our previous studies demonstrated that ppl05 is distinct from pp125FAK, although both ppl05 and pp125FAK are tyrosine phosphorylated via similar kinetics by the engagement of oL4 [~l integrin in H9 ceils (12). Given the fact that ppl05 is one of the major proteins that is tyrosine phosphorylated by [31 integrin stimulation in peripheral T cells, ppl05 may play an important role in [31 integfin-mediated signaling in T cells.Recently, Sakai et al. (13) cloned the cDNA ofpl30Cas (Crk-associated substrate), p130Cas was originally identified as a tyrosine-phosphorylated 130 kD protein in the p60 v-src-or p47V-Crk-transformed fibroblasts. The deduced amino acid sequence of pl30Cas revealed that p130Cas contained one Src homology (SH) 3 domain in the NH zterminal region and multiple putative binding sites of SH2 domains. Tyrosine phosphorylated pl30Cas bound to Crk, and the deduced amino acid sequence of p130Cas contained multiple binding motifs of the Crk SH2 domain. Crk can bind to guanine nucleotide-releasing factors son of sevenless (SOS) and C3G by the SH3 domain of Crk (14,15). SOS and C3G are involved in the activation of Kas

Role of the adapter protein CRKL in signal transduction of normal hematopoietic and BCR/ABL-transformed cells

“…29,30 CAS (for Crk-associated substrate) was cloned as a major 130 kDa tyrosine phosphorylated protein in response to v-crk transformation. 27 Currently, there are three CAS-related molecules (the 130 kDa protein CAS, the 110 kDa protein HEF1/CAS-L, 67,68 and the 95 kDa protein SIN/EFS 69,70 ). The structure for CAS-family members includes an amino-terminal SH3 domain, multiple YXXP motifs (substrate domain), and potential SRC-binding sites at the Cterminus.…”

Phosphorylation of human enhancer of filamentation (HEF1) on serine 369 induces its proteasomal degradation

“…Later on, its role in intracellular signalling and regulation of cytoskeleton has been further characterized. Several reports demonstrated that HEF1 is mainly expressed in lymphoid and epithelial cells [2,3]. It has been implicated in signalling pathways initiated by ligation of integrins or antigen on BCR or TCR [2][3][4][5].…”

HEF1-Aurora A Interactions: Points of Dialog between the Cell Cycle and Cell Attachment Signaling Networks

“…In contrast, HEF1 expression varies considerably between different cell types and tissues. 71,72,96,97 It is most abundant in vivo in tissues with polarized cell populations, including epithelial cells, neuronal and glial cells, and lymphoid cells, and its signaling action may be particularly important in these cell lineages. 97,98 p130Cas is abundant at all phases of cell cycle.…”