Platelet aggregation, storage pool deficiency, and protein phosphorylation in mice with Chediak-Higashi syndrome

Abstract

SUMMARY The beige (bgJ/bgJ) mouse is a well-described murine model of Chediak-Higashi syndrome. Platelet function was examined in normal and beige mice to better characterize the defective aggregation response in platelets from mice with Chediak-Higashi syndrome. Platelet aggregation after collagen, thrombin, and phorbol-12-myristate 13-acetate stimulation was significantly (P < 0.025) decreased in platelets from beige mice, relative to platelets from normal mice. Compared with beige and normal mice, those heterozygous for the bg trait had intermediate responses to collagen and thrombin, but not phorbol-12-myristate 13-acetate. The defect(s) in aggregation of platelets from beige mice was associated with a dense granule storage pool deficiency and decreased stores of serotonin and adenine nucleotides in platelets. Mice heterozygous for the bg trait had normal platelet serotonin and adenine nucleotide concentrations. Platelets from beige mice were approximately 10 times more sensitive to prostacyclin inhibition of collagen-induced aggregation than were platelets from control mice. However, a significant difference in platelet cyclic AMP concentration was not apparent between beige and normal mice after prostacyclin stimulation. Platelet endoperoxide synthesis measured by quantification of thromboxane B2, was normal in beige mice. Protein phosphorylation patterns in mouse platelets were similar to those seen in human platelets. Thrombin and collagen-induced [32P] phosphorylation of 40- and 20-kD proteins in platelets from normal and beige mice was similar. Results indicate that the biochemical defect(s) in platelet function in beige mice is partially attributable to storage pool deficiency and does not result in an absolute defect in phosphorylation of 40- and 20- kD proteins.