Immunoreactive glycogen-binding subunit of protein phosphatase-1 in human skeletal muscle.
In rabbit muscle, analyzed by Western blot, the glycogen-bound protein phosphatase-1 (PP-1G) is composed of a 37-kilodalton (kDa) catalytic subunit complexed to a 160-kDa glycogen-binding subunit (G-subunit) responsible for the interaction of PP-1G with glycogen. PP-1G has not been characterized in humans. In the present study, G-subunit was identified in human muscle extracts by Western blot using an antibody raised against a sequence (the phosphoregulatory domain) of the rabbit muscle G-subunit. The human G-subunit was also a 160-kDa protein by Western blot. When the G-subunit content of skeletal muscle was quantitated in 17 Pima Indians with a wide range of insulin sensitivities determined during euglycemic clamps, there was a significant negative correlation (r = -0.55; P = 0.02) between the G-subunit content and in vivo insulin-mediated glucose disposal rates. The results suggest that insulin resistance is associated with an increased content and/or immunoreactivity of G-subunit in human muscle.
Nyomba
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BL
Clinical Diabetes and Nutrition Section, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Phoenix, Arizona 85016.
Mott
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DM
D000328:Adult; D000818:Animals; D001665:Binding Sites; D001786:Blood Glucose / Q000378:metabolism; D015153:Blotting, Western; D005260:Female; D006003:Glycogen / Q000378:metabolism*; D006801:Humans; D007198:Indians, North American; D007328:Insulin / Q000494:pharmacology; D007333:Insulin Resistance; D008297:Male; D009132:Muscles / Q000201:enzymology*; D010749:Phosphoprotein Phosphatases / Q000737:chemistry* / Q000378:metabolism; D054645:Protein Phosphatase 1; D011817:Rabbits
D001786:Blood Glucose; D007328:Insulin; D006003:Glycogen; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1