Insulin-induced decrease in 5'-nucleotidase activity in skeletal muscle membranes.
Insulin releases inositol phosphoglycans from myocytes in culture [(1986) Science 233, 967-972], which display insulinomimetic activity. Because 5'-nucleotidase is anchored to the membrane through inositol-containing phospholipid glycans, we investigated whether insulin could release the enzyme from the membrane. Membranes prepared from hindquarter muscles of rats perfused with insulin showed a 23% decrease in 5'-nucleotidase activity. Isolated membranes from muscle exposed to insulin in vitro also showed a small but reproducible decrease (9%) in 5'-nucleotidase activity relative to unexposed controls. Phospholipase C from Staphylococcus aureus released 60% of the membrane-bound 5'-nucleotidase. We propose that insulin may activate an endogenous phospholipase C that cleaves phospholipid-glycan-anchored proteins.
Klip
A
A
Department of Cell Biology, Hospital for Sick Children, Toronto, Canada.
Ramlal
T
T
Douen
A G
AG
Burdett
E
E
Young
D
D
Cartee
G D
GD
Holloszy
J O
JO
D015720:5'-Nucleotidase; D000818:Animals; D017301:Ca(2+) Mg(2+)-ATPase / Q000378:metabolism; D002462:Cell Membrane / Q000187:drug effects / Q000201:enzymology; D007328:Insulin / Q000494:pharmacology*; D008297:Male; D009132:Muscles / Q000187:drug effects / Q000201:enzymology*; D009708:Nucleotidases / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013211:Staphylococcus aureus / Q000201:enzymology; D010738:Type C Phospholipases / Q000378:metabolism / Q000494:pharmacology
D007328:Insulin; D009708:Nucleotidases; D015720:5'-Nucleotidase; D010738:Type C Phospholipases; D017301:Ca(2+) Mg(2+)-ATPase