Showing papers on "Protease-activated receptor 2 published in 1983"

The human C3b receptor.

Abstract: The cellular receptor for the C3b fragment of the third component of complement is a 205,000 molecular weight glycoprotein expressed by erythrocytes, polymorphonuclear leukocytes, monocytes, B lymphocytes, a subset of T lymphocytes and glomerular podocytes. The receptor molecule is a potent inhibitor of complement activation by both the alternative and classical pathways. It serves as a cofactor in the proteolytic degradation of C3b bound to immune complexes. On neutrophils and monocytes, the receptor enhances immunoglobulin-dependent phagocytosis of opsonized particles and triggers internalization of soluble ligands bearing C3b. The number of C3b receptor molecules expressed on erythrocytes is genetically determined and was found to be low in patients with systemic lupus erythematosus: these abnormalities when associated with a low number of receptors in the kidney of patients with non-systemic lupus erythematosus nephritis may predispose to immune complex diseases.

Acetylcholine receptor turnover in clonal muscle cells: role of plasmin and effects of protease inhibitors.

Abstract: Characteristics of acetylcholine receptors were evaluated in G8-1, a continuous skeletal muscle line. Peak binding of 125I-alpha-bungarotoxin was in 10-day-old contractile myotubes at 4-8 nm. Turnover was studied using two different methods; both indicated half-times as little as half as long as previously reported for primary cultures. The effects of a variety of protease inhibitors on receptor turnover were assessed to determine if G8-1 receptors were less stable or turned over faster because of increased neutral protease activity. Leupeptin, antipain, and chloroquine markedly slowed receptor degradation. Inhibitors of plasmin or plasminogen activator had definite but less dramatic effects on receptor turnover. Results from studies in which plasmin was increased in the tissue culture media indicated that a small but definite acceleration of receptor turnover occurred. In clonal G8-1 cells, total number of acetylcholine receptors is controlled by negative feedback and although the major pathway for receptor degradation is lysosomal, plasmin may play a role in initiating receptor internalization.

Ia antigen: a murine B lymphocyte receptor for transformed cell induction of interferon-alpha/beta.

Abstract: A receptor on the surface of nonsensitized mouse spleen cells that recognizes a glycoprotein from transformed mouse L-929 cells is described. The interaction of the receptor and glycoprotein inducer results in the production of MoIFN alpha/beta. An assay was developed to assess certain biologic and physicochemical characteristics of the receptor. The receptor and glycoprotein inducer bound in a concentration-dependent manner, which tends to indicate a direct interaction between the two. The receptor was not ubiquitous; spleen cells but not normal mouse embryo cells appeared to be the source. It was specific for MoIFN alpha/beta inducers from transformed cells, but not from other MoIFN alpha/beta or gamma inducers such as NDV, LPS, PWM, or SEA. The receptor appeared to be a cell surface protein in that its activity was abolished by trypsinization of whole spleen cells. Previous studies indicated that the receptor was probably located on B cells. Gel filtration indicated that the receptor had a m.w. of 30,000 to 60,000. Because the receptor appeared to be: 1) B lymphocyte associated, 2) a surface protein, and 3) 30,000 to 60,000 daltons, a similarity to Ia antigen was suggested. This possibility was confirmed by showing binding of the receptor to an anti-IaK antibody-Sepharose affinity column. PAGE analysis of the affinity-purified receptor revealed a single protein band with a m.w. of approximately 60,000. ELISA of the above gel slices with anti-Ia antibody further confirmed the specificity of the column. A physical association of the receptor and inducer was demonstrated by showing binding of the glycoprotein inducer to a receptor (Ia antigen)-Sepharose affinity column. Furthermore, the receptor (Ia antigen) was highly purified by a glycoprotein inducer-Sepharose affinity column.