Human platelet calmodulin-binding proteins: identification and Ca/sup 2 +/-dependent proteolysis upon platelet activation

Journal Article · Tue May 19 04:00:00 EDT 1987 · Biochemistry; (United States)

DOI:https://doi.org/10.1021/bi00384a017· OSTI ID:5878052

Wallace, R W; Tallant, E A; McManus, M C

Calmodulin-binding proteins have been identified in human platelets by using Western blotting techniques and /sup 125/I-calmodulin. Ten distinct proteins of 245, 225, 175, 150, 90, 82 (2), 60, and 41 (2) kilodaltons (kDa) bound /sup 125/I-calmodulin in a Ca/sup 2 +/-dependent manner; the binding was blocked by ethylene glycol bis(..beta..-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA), trifluoperazine, and nonradiolabeled calmodulin. Proteins of 225 and 90 kDa were labeled by antisera against myosin light chain kinase; 60- and 82-kDa proteins were labeled by antisera against the calmodulin-dependent phosphatase and caldesmon, respectively. The remaining calmodulin-binding proteins have not been identified. Calmodulin-binding proteins were degraded upon addition of Ca/sup 2 +/ to a platelet homogenate; the degradation could be blocked by either EGTA, leupeptin, or N-ethylmaleimide which suggests that the degradation was due to a Ca/sup 2 +/-dependent protease. Activation of intact platelets by thrombin, adenosine 5'-diphosphate, and collagen under conditions which promote platelet aggregation also resulted in limited proteolysis of calmodulin-binding proteins including those labeled with antisera against myosin light chain kinase and the calmodulin-dependent phosphatase. Activation by the Ca/sup 2 +/ ionophores A23187 and ionomycin also promoted degradation of the calmodulin-binding proteins in the presence of extracellular Ca/sup 2 +/. The data indicate that limited proteolysis of Ca/sup 2 +//calmodulin-regulated enzymes also occurs in the intact platelet and suggest that the proteolysis is triggered by an influx of extracellular Ca/sup 2 +/ associated with platelet aggregation.

• Research Organization: Univ. of Alabama, Birmingham
• OSTI ID: 5878052
• Journal Information: Biochemistry; (United States), Journal Name: Biochemistry; (United States) Vol. 26:10; ISSN BICHA
• Country of Publication: United States
• Language: English

Related Subjects

550601* -- Medicine-- Unsealed Radionuclides in Diagnostics
62 RADIOLOGY AND NUCLEAR MEDICINE
ALKALINE EARTH METAL COMPOUNDS
AUTORADIOGRAPHY
BETA DECAY RADIOISOTOPES
BIOLOGICAL MATERIALS
BLOOD
BLOOD CELLS
BLOOD PLATELETS
BODY FLUIDS
CALCIUM CHLORIDES
CALCIUM COMPOUNDS
CALCIUM HALIDES
CATIONS
CHARGED PARTICLES
CHEMICAL ACTIVATION
CHEMICAL REACTIONS
CHLORIDES
CHLORINE COMPOUNDS
DAYS LIVING RADIOISOTOPES
DECOMPOSITION
ELECTRON CAPTURE RADIOISOTOPES
ELECTROPHORESIS
HALIDES
HALOGEN COMPOUNDS
INTERMEDIATE MASS NUCLEI
IODINE 125
IODINE ISOTOPES
IONS
ISOTOPES
LABELLED COMPOUNDS
MATERIALS
NUCLEI
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
PROTEINS
PROTEOLYSIS
RADIOISOTOPES