Integrin-mediated cell adhesion induces various biological events such as cell proliferation, survival, migration, cytokine production, and cytoskeleton reorganization (1-7). Despite the significance of these events, signal transduction pathways of integrins have not been fully understood. One of the approaches for integrin-mediated signal transduction is to study the proteins that are localized to focal adhesions.Focal adhesions are the sites where cells attach to substrata via integrin-extracellular matrix binding (7,8). Various cytoskeletal proteins and signaling molecules such as focal adhesion kinase (FAK), 1 paxillin, vinculin, talin, p130 Cas , and tensin, are accumulated in the cytoplasmic part of focal adhesions (7-10). More interestingly, focal adhesions are strongly stained by immunohistochemical analysis with anti-phosphotyrosine mAb (7, 10). Several proteins localized to focal adhesions such as FAK, paxillin, and p130Cas , are tyrosine phosphorylated following integrin stimulation (7, 9, 10). When tyrosine phosphorylated, these proteins bind to signaling molecules such as Crk, Nck, GRB2, Src, which contain Src homology (SH) 2 domain (7, 10). Paxillin, a 68-kDa cytoskeletal protein, is one of these focal adhesion proteins (11-13) and has two functions in integrin-mediated signal transduction. First, paxillin appears to be the major entity that recruits two binding proteins, FAK,, to focal adhesions (16,17). Second, paxillin is tyrosine phosphorylated following integrin stimulation in a FAK-dependent manner, and then binds to the Crk SH2 domain (15,18). Thus, paxillin is involved in recruitment of FAK to focal adhesions, tyrosine phosphorylated by FAK and/or a kinase(s) that is associated with FAK, and then works as a docking protein in integrin-mediated signal transduction. Hydrogen peroxide-inducible clone (hic)-5 was initially identified as a gene which was induced by transforming growth factor ␤1 or by H 2 O 2 (19). The expression of hic-5 mRNA was augmented in the in vitro senescent process of human diploid fibroblasts (19). The forced overexpression of Hic-5 induced growth retardation, senescence-like morphology such as the enlarged and flattened morphology, and the increased expression of p21/WAF1/Cip1/sdi1 and extracellular matrix-related proteins such as fibronectin (FN), collagen, and collagenase (20). These findings suggest that Hic-5 is involved in very interesting function in the senescent process and in transforming growth factor ␤1-mediated signal transduction. However, the nature of Hic-5 function has not been clarified yet. Structurally, Hic-5 contains four LIM domains in the C-terminal half and LD domains in the N-terminal half (19,21). These domains are conserved in paxillin, and the four LIM domains of Hic-5 and paxillin share 62% homology (17, 19 -21). These structural homology with paxillin suggested that Hic-5 is localized to focal adhesions and involved in integrin-mediated signal transduction. Recently, Matsuya et al. (21) reported that Hic-5 bound to Cak ␤, a FAKrelated tyro...

Cas-L (pp105), a Crk-associated substrate (p130Cas )-related protein, was first identified as a 105-kDa protein that is tyrosine-phosphorylated following ␤1 integrin cross-linking in T cells. Cas-L contains possible multiple binding sites for the Src homology (SH) 2 domains of various signaling molecules, and appears to be involved in signal transduction through phosphorylated tyrosine-mediated protein-protein interaction. Since Cas-L is preferentially expressed in lymphocytes, it is conceivable that Cas-L plays an important role in lymphocytespecific signals. Here, we show the involvement of Cas-L in the T cell receptor (TCR)/CD3 signaling pathway. Cas-L is transiently phosphorylated following CD3 cross-linking, and tyrosine-phosphorylated Cas-L binds to Crk and C3G. Furthermore, a Cas-L mutant that lacks the SH3 domain, the binding site for focal adhesion kinase (FAK), is also tyrosine-phosphorylated upon CD3 cross-linking, but not upon ␤1 integrin crosslinking, suggesting that FAK is not involved in CD3-dependent Cas-L phosphorylation. Taken together, the present study indicates a novel signaling pathway mediated by tyrosine-phosphorylated Cas-L upon the TCR/CD3 stimulation. T cell receptor (TCR)1 -antigen binding induces gene expression, cytokine production, and cell proliferation in T lymphocytes (1). These TCR-dependent signals are mediated by tyrosine phosphorylation of various proteins including CD3␦, CD3⑀, CD3␥, Shc, Vav,. These signaling molecules appear to be involved in the phosphorylated tyrosinemediated protein-protein interaction and the recruitment of the other signaling molecules containing Src homology (SH) 2 domains (3). The recruitment of these signaling molecules is essential to induce various signals to the downstream events such as the activation of mitogen-activated protein kinases, Ca 2ϩ influx, and transcriptional activation of various genes (1).Thus, protein tyrosine phosphorylation plays a key role during the initial phase of TCR-mediated T cell activation. However, the essential phosphorylated molecule and the precise function of each phosphorylated molecule for these signaling pathwayshave not yet been clarified. Cas-L (pp105) was first identified as a 105-kDa protein that is tyrosine-phosphorylated upon ␤1 integrin cross-linking (4). Cas-L belongs to Cas-family along with p130Cas and Efs/Sin (5-7). The three proteins share the structural characteristics of an N-terminal SH3 domain, followed by multiple (8 to 15) YXXP motifs, which are putative binding sites for the Crk SH2 domain, and a conserved YDYVHL sequence that possibly binds to the Src SH2 domain. (5-7). Cas-L was shown to associate with the C-terminal domain of focal adhesion kinase (FAK), a cytoplasmic tyrosine kinase that is localized to focal adhesions (5,8). Recently, we reported that the conserved YDYVHL sequence of Cas-L was phosphorylated by FAK following ␤1 integrin cross-linking and that an Src family tyrosine kinase is recruited to the phosphorylated YDYVHL sequence and causes further tyrosine phosphorylation of ...

Integrin-ligand binding induces the tyrosine phosphorylation of various proteins including focal adhesion kinase (pp125 FAK ) and Crk-associated substrate (Cas). FAK is activated and autophosphorylated by the ligation of integrins, although the substrate of FAK has not been revealed. We show here that p130Cas and Cas-L are FAK substrates. FAK directly phosphorylates Cas proteins primarily at the YDYVHL sequence that is conserved among all Cas proteins. Furthermore, the phosphorylated YDYVHL sequence is a binding site for Src family protein-tyrosine kinases, and the recruited Src family kinase phosphorylates the other tyrosine residues within Cas. The Cas-L YDYVHL sequence is phosphorylated upon integrin-ligand binding, and this integrin-mediated tyrosine phosphorylation is inhibited by the cotransfection of the FAK COOH-terminal domain that does not contain a kinase domain. These findings strongly suggest that FAK initiates integrin-mediated tyrosine phosphorylation of Cas proteins; then, Src family tyrosine kinases, which are recruited to phosphorylated Cas and FAK, further phosphorylate Cas proteins.Integrin-ligand binding induces various biological and biochemical signals in addition to cell adhesion (1-4). We and others showed the costimulatory effect of the ligation of ␤1 integrin in CD3-dependent T cell proliferation, indicating that integrin-ligand binding can promote cell proliferation (5, 6). To reveal the mechanism of the integrin-mediated biological signals, numbers of laboratories have studied the role of protein tyrosine phosphorylation in various cell types (7-10). However, how proteins are tyrosine phosphorylated upon integrin stimulation is currently unknown. Since integrin themselves are not a tyrosine kinase, a tyrosine kinase(s) that is functionally linked to integrins is essential for the integrin signaling pathway.One of the prime candidates for this tyrosine kinase is focal adhesion kinase, pp125 Cas is a 120 -130-kDa protein that was first identified as a highly tyrosine-phosphorylated protein in both v-Src-and v-Crk-transformed fibroblasts (25-27). Subsequently, a 105-110-kDa p130Cas -related protein (Cas-L or HEF1) was identified as a 105-kDa protein that is tyrosine phosphorylated upon the ligation of ␤1 integrins in T lymphocytes (28,29). Furthermore, an 83-kDa Cas-related protein, Efs (or Sin), was reported as the binding proteins for the Src homology 3 (SH3) domains of Fyn and Src (30,31). All Cas proteins contain one SH3 domain in the NH 2 -terminal region, and they all contain multiple putative binding sites for Src homology 2 (SH2) domains, including 8 -15 binding sites for the Crk SH2 domain. All three Cas proteins also contain a YDYVHL sequence, which is a potential binding site for the Src SH2 domain (31, 32). We and others reported that both p130 Cas and Cas-L were tyrosine phosphorylated upon the ligation of integrins and that tyrosine-phosphorylated Cas proteins bind to the SH2 domain-containing proteins Crk, Nck, and SHP-2 (28, 33, 34). Furthermore, Cas proteins bind direc...

The world's first non-phosgene polycarbonate process from CO 2 has been developed and industrialized by Asahi Kasei Corporation (Japan). Hitherto, all polycarbonates (PCs) have been produced using CO as a raw material. Among them, most PCs have been produced by so-called the "phosgene process" using highly toxic phosgene (COCl 2 ) and large amounts of solvents (probable human carcinogen CH 2 Cl 2 and water). The phosgene process has many environmental and safety problems. However, technological barriers have hindered realizing the non-phosgene PC process. The Asahi Kasei Process has not only solved the problems of the phosgene process but also contributed to sustainability (reduction of CO 2 emission, materials saving, and energy saving). High-quality PC and high-purity monoethylene glycol (MEG) are produced in high yields, respectively, without waste and wastewater, starting from CO 2 , ethylene oxide (EO), and bisphenol A (BPA). In the monomer (diphenyl carbonate: DPC) production process, innovative reactive distillation process, and in the melt polymerization process, a gravityutilized non-agitation reactor had been developed, respectively. The Asahi Kasei Process has been expanding worldwide, and 1.07 million tons of PC will be produced in 2019. The Green Sustainable Chemical Process has been changing the PC production world. In this review, the Asahi Kasei Process and perspective of the present PC production processes together with discriminating and detailed comparisons are described.