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Stimulation by Mammalian Insulin of Glycogen Metabolism in a Wall-Less Strain of Neurospora crassa^*

STEPHEN E. FAWELL, MAUREEN A. McKENZIE, NORMA J. GREENFIELD, FOLUSO ADEBODUN, FRANK JORDAN and JOHN LENARD

Department of Physiology and Biophysics, University of Medicine and Dentistry of New Jersey-Robert Wood Johnson Medical School (S.E.F., M.A.M., N.J.G., J.L.) Piscataway, New Jersey 08854-5635
the Department of Chemistry, Rutgers, The State University (F.A., F.J.) Newark, New Jersey 07102

Address requests for reprints to: Dr. John Lenard, Department of Physiology and Biophysics, University of Medicine and Dentistry of New Jersey-Robert Wood Johnson Medical School, 675 Hoes Lane, Piscataway, New Jersey 08854.

Abstract

Addition of bovine insulin to cells of the wallless variant FGSC4761 of Neurospora crassa ("slime") produced several significant effects on glycogen metabolism. 1) Intracellular levels of the glycogen precursor UDP-glucose decreased 17–18% (P < 0.01) within 30 min of insulin addition. 2) Cells grown with insulin possessed 40% more glycogen than did control cells. 3) The incorporation of ¹⁴C-labeled glucose into glycogen increased 41% after 30-min treatment with 100 nM bovine insulin (P < 0.01). 4) Insulin treatment of the cells caused activation of the enzyme glycogen synthase from a glucose-6- phosphate-dependent form to an independent form. Half-maximum activation occurred with 2 nM insulin. These are similar to insulin-induced effects in some mammalian cells. In contrast, no insulin-induced effect on glucose transport could be demonstrated in these cells. (Endocrinology 122: 518–523, 1988)

Footnotes

^* This work was supported in part by NIH Grants AI-13002 and GM-34050 and the Rutgers University Busch Fund.

Present address: National Institute of Diabetes, Digestive and Kidney Disease, Building 10, Room 8S-23, National Institutes of Health, Bethesda, Maryland 20892.

Received May 8, 1987.