AJP - Renal Physiology, Vol 253, Issue 5 841-F847, Copyright © 1987 by American Physiological Society

ARTICLES

Distribution of IGF receptors in the plasma membrane of proximal tubular cells

M. R. Hammerman and S. Rogers
Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri 63110.

To characterize the distribution of receptors for insulin-like growth factors I and II (IGF I and II) in the plasma membrane of the renal proximal tubular cell, we measured binding of 125I-labeled IGF I and 125I-labeled IGF II to proximal tubular basolateral and brush-border membranes and characterized IGF I-stimulated phosphorylation of detergent-solubilized membranes. 125I-IGF I bound primarily to a 135,000 relative molecular weight (Mr) protein and IGF II to a 260,000 Mr protein in isolated membranes. Binding of 125I-IGF I was severalfold greater in basolateral than in brush-border membranes. IGF I-stimulated phosphorylation of the 92,000 Mr beta-subunit of its receptor could be demonstrated only in basolateral membranes. These findings are consistent with an asymmetrical distribution of receptors for IGF I in the plasma membrane of the renal proximal tubular cell, localization being primarily on the basolateral side. In contrast, binding of 125I-IGF II to isolated basolateral and brush-border membranes was equivalent, suggesting that receptors for this peptide are distributed more symmetrically in the plasma membrane. Our findings suggest that the actions of IGF I in proximal tubule are mediated via interaction of circulating peptide with specific receptors in the basolateral membrane. However, our findings establish the potential for actions of IGF II to be exerted in proximal tubule via interaction with both basolateral and/or brush-border membrane receptors.

This article has been cited by other articles:

				P. R. Cutillas, R. J. Chalkley, K. C. Hansen, R. Cramer, A. G. W. Norden, M. D. Waterfield, A. L. Burlingame, and R. J. Unwin The urinary proteome in Fanconi syndrome implies specificity in the reabsorption of proteins by renal proximal tubule cells Am J Physiol Renal Physiol, September 1, 2004; 287(3): F353 - F364. [Abstract] [Full Text] [PDF]

				C. B. Woda, N. Halaihel, P. V. Wilson, A. Haramati, M. Levi, and S. E. Mulroney Regulation of renal NaPi-2 expression and tubular phosphate reabsorption by growth hormone in the juvenile rat Am J Physiol Renal Physiol, July 1, 2004; 287(1): F117 - F123. [Abstract] [Full Text] [PDF]

				K. Morrisey, R. A. Evans, L. Wakefield, and A. O. Phillips Translational Regulation of Renal Proximal Tubular Epithelial Cell Transforming Growth Factor-{beta}1 Generation by Insulin Am. J. Pathol., November 1, 2001; 159(5): 1905 - 1915. [Abstract] [Full Text] [PDF]

				N. Obermuller, B. Kranzlin, W. F. Blum, N. Gretz, and R. Witzgall An endocytosis defect as a possible cause of proteinuria in polycystic kidney disease Am J Physiol Renal Physiol, February 1, 2001; 280(2): F244 - F253. [Abstract] [Full Text] [PDF]

				H. Murer, N. Hernando, I. Forster, and J. Biber Proximal Tubular Phosphate Reabsorption: Molecular Mechanisms Physiol Rev, October 1, 2000; 80(4): 1373 - 1409. [Abstract] [Full Text] [PDF]

				K. Amsler and S. K. Kuwada Membrane receptor location defines receptor interaction with signaling proteins in a polarized epithelium Am J Physiol Cell Physiol, January 1, 1999; 276(1): C91 - C101. [Abstract] [Full Text] [PDF]