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Shinya Katsutani

Publications and source records attributed to Shinya Katsutani.

4 recordsLinked to original sources
PubMed2004

Monoclonal antibody IAC-1 is specific for activated alpha2beta1 and binds to amino acids 199 to 201 of the integrin alpha2 I-domain.

In this study we describe the first monoclonal antibody, integrin activated conformation-1 (IAC-1), to recognize the active form of the platelet-collagen receptor, the integrin alpha(2)beta(1). IAC-1 has the following properties: (1) IAC-1 fails to bind to resting platelets but readily interacts with platelets stimulated by the glycoprotein VI-specific agonist, convulxin, and by other agonists; (2) similar concentration response relationships for binding of IAC-1 and soluble collagen were observed in convulxin-stimulated platelets; (3) the epitope for IAC-1 is T199Y200K201, which is located at the opposite site of the metal ion-dependent adhesion site in a region not involved in the I-domain "shifts" that occur upon ligand binding; (4) IAC-1 strongly binds to recombinant alpha(2) I-domain, therefore suggesting that the neo-epitope appears to be exposed by an "unmasking" of I-domain-covering regions upon activation; (5) IAC-1 binds to platelets during adhesion to collagen under shear conditions, demonstrating activation of alpha(2)beta(1); (6) as IAC-1 does not interfere with platelet-collagen binding, it defines a new class of antibodies that is distinct from those belonging to the "cation- and ligand-induced binding sites" (CLIBSs) and the "ligand mimetic" group. These characteristics make IAC-1 a very powerful tool to study alpha(2)beta(1) activation under dynamic and physiologically relevant conditions.

Amino Acid Sequence↗
PubMed2003

Thrombospondin-bound integrin-associated protein (CD47) physically and functionally modifies integrin alphaIIbbeta3 by its extracellular domain.

Integrin-associated protein (IAP/CD47) is a receptor for the C-terminal cell binding domain of thrombospondin (TS). A peptide from the C-terminal cell binding domain, KRFYVVMWKK (4N1K) binds to IAP and stimulates the integrin-dependent cell functions, including platelet aggregation. We investigated the mechanism by which TS-bound IAP modulates the affinity of platelet integrin, alphaIIbbeta3. Platelet aggregation induced by 4N1K was not completely inhibited by energy depletion with sodium azide and 2-deoxy-d-glucose, although ADP or collagen-induced platelet response was completely inhibited. The binding of ligand-mimetic antibody PAC1 to alphaIIbbeta3 was also induced in the energy-depleted platelets. In the transfected Namalwa cells, 4N1K induced activation of the alphaIIbbeta3 with mutated beta3 (Ser-752 to Pro), which is a non-responsive form to inside-out signaling, as well as wild type alphaIIbbeta3. The truncated form of IAP with only the extracellular immunoglobulin-like (Ig) domain was sufficient for the activation of alphaIIbbeta3 in Chinese hamster ovary cells, although the IAP-mediated intracellular signaling was abolished, which was monitored by the absence of down-regulation of mitogen-activated protein kinase phosphorylation. Furthermore, the soluble recombinant Ig domain of IAP induced PAC1 binding to alphaIIbbeta3 on Chinese hamster ovary cells when added with 4N1K. Physical association between the soluble recombinant Ig domain of IAP and purified alphaIIbbeta3 was detected in the presence of 4N1K. These data indicate that the extracellular Ig domain of IAP, when bound to TS, interacts with alphaIIbbeta3 and can change alphaIIbbeta3 in a high affinity state without the requirement of intracellular signaling. This extracellular event would be a novel mechanism of affinity modulation of integrin.

Amino Acid Sequence↗
PubMed2002

Novel alternatively spliced form of beta(3)-endonexin.

beta(3)-Endonexin is a binding protein to the cytoplasmic tail of beta(3) integrin and can activate alpha(IIb)beta(3) in Chinese hamster ovary (CHO) cells. Initially, two forms were identified, and only the shorter form showed the function. However, it localized mainly to the nucleus because of a nuclear localization signal (K(62)RKK). We identified two additional forms of beta(3)-endonexin. One encoded 177 amino acids and was identical to the protein previously reported as a thyroid hormone receptor-binding protein. The other is a novel shortest form encoding 62 amino acids. Although the novel form lacked nuclear localization signal and was observed diffusely in the cytoplasm of transfected cells, this form did not show interaction with beta(3) integrin. Then, the ideal form as an integrin modulator was not found among these isoforms. Nevertheless, when the nuclear localization signal of the shorter form was disrupted, beta(3)-endonexin was localized near the cell surface and modulated the affinity of alpha(IIb)beta(3) more intensively. These results suggest the presence of various isoforms and the relationship between subcellular localization and integrin-activating function of beta(3)-endonexin.

Alternative Splicing↗