Insulin stimulates a novel GTPase activity in human platelets
1987; Wiley; Volume: 216; Issue: 1 Linguagem: Inglês
10.1016/0014-5793(87)80763-9
ISSN1873-3468
AutoresDebra J. Gawler, Miles D. Houslay,
Tópico(s)Lipid Membrane Structure and Behavior
ResumoInsulin stimulated the activity of a high‐affinity GTPase activity in human platelet membranes some 62% over that of the basal activity. Half‐maximal stimulation ( K a ) was achieved with 3.1 nM insulin. The K m for GTP of the insulin‐stimulated GTPase was 0.6 μM GTP. Treatment of isolated platelet membranes with cholera toxin, but not pertussis toxin, blocked insulin's ability to stimulate GTPase activity. Cholera toxin acted as a more potent inhibitor of the insulin‐stimulated GTPase activity than that of the GTPase activity of the stimulatory guanine nucleotide regulatory protein, G s , as monitored by stimulation using prostaglandin E 1 (PGE 1 ). Mixed ligand experiments showed that insulin stimulated GTPase activity in an additive fashion to GTPase activity stimulated by PGE 1 , due to G s ; by adrenaline (+ propranolol), due to the inhibitory guanine nucleotide regulatory protein, G i and by vasopressin, which stimulates the putative ‘G p ’, a G‐protein suggested to control the stimulation of inositol phospholipid metabolism. Insulin thus appears to stimulate a novel high‐affinity GTPase activity in human platelet membranes. This may reflect the functioning of the putative G ins , a guanine nucleotide regulatory protein which has been suggested to mediate certain of insulin's actions on target tissues.
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