Endocrinology, Vol 122, 518-523, Copyright © 1988 by Endocrine Society

ARTICLES

Stimulation by mammalian insulin of glycogen metabolism in a wall-less strain of Neurospora crassa

SE Fawell, MA McKenzie, NJ Greenfield, F Adebodun, F Jordan and J Lenard
Department of Physiology and Biophysics, University of Medicine and Dentistry of New Jersey-Robert Wood Johnson Medical School, Piscataway 08854-5635.

Addition of bovine insulin to cells of the wall-less 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 less than 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 less than 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.