✦ LIBER ✦

Receptor-mediated endocytosis and degradation of insulin-like growth factor I and II in neonatal rat astrocytes

✍ Scribed by M. Auletta; F. C. Nielsen; Dr. S. Gammeltoft

Publisher: John Wiley and Sons
Year: 1992
Tongue: English
Weight: 657 KB
Volume: 31
Category: Article
ISSN: 0360-4012
DOI: 10.1002/jnr.490310103

No coin nor oath required. For personal study only.

✦ Synopsis

Receptor-mediated internalization and degradation of insulin-like growth factors, IGF-I and IGF-11, were studied in primary cultures of neonatal rat astrocytes. Surface-bound IGF-I1 was rapidly internal-ize& and 80% of cell-associated radioactivity was located intracellularly after 30 min. IGF-I was internalized at a slower rate, and only 40% of cell-associated radioactivity was inside the cell after 30 min. A pulse-chase experiment demonstrated that 55% and 70% of internalized IGF-I and IGF-11, respectively, was degraded to free amino acids after a 3-hr chase. Lysosomal and protease inhibitors had different effects on the binding, internalization, and processing of IGF-I and IGF-11. Inhibition of lysosomal acidification by chloroquine increased the amounts of surface-bound IGF-I1 and intracellular IGF-I and reduced the degradation of IGF-I. The chelating agent phenanthroline increased the surface binding of IGF-I and IGF-I1 and internalization of IGF-I1 and reduced the degradation of IGF-I and IGF-11. Finally, receptor-bound IGF-I1 on the cell surface was decreased with increasing cell density, whereas IGF-I binding was unaltered. Our data suggest that cellsurface expression of IGF-I receptors and IGF-I1 receptors is regulated by different mechanisms and that receptor-bound IGF-I and IGF-I1 are trafficked and processed by different intracellular pathways in neonatal rat astrocytes.

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