HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Opresko, L. K. Articles by Wiley, H. S. Search for Related Content PubMed PubMed Citation Articles by Opresko, L. K. Articles by Wiley, H. S. Social Bookmarking                      What's this?

J. Biol. Chem., Vol. 262, Issue 9, 4116-4123, Mar, 1987

Receptor-mediated endocytosis in Xenopus oocytes. II. Evidence for two novel mechanisms of hormonal regulation

LK Opresko and HS Wiley

Xenopus oocytes exhibit enhanced rates of vitellogenin (VTG) endocytosis following exposure to insulin in vitro and human chorionic gonadotropin in vivo. We investigated this phenomenon using kinetic and steady state analyses and found that the stimulation of VTG uptake was not due to an increase in surface VTG receptors. Instead, both hormones acted by stimulating the specific internalization rate (ke) of the VTG receptor, although by apparently different mechanisms. The stimulation of ke by insulin was most obvious at low levels of receptor occupancy. Insulin also increased the affinity of the VTG receptor for its ligand. Both hormones increased the rate of fluid phase endocytosis, but the magnitude of stimulation was not sufficient to account for the observed increase in VTG uptake. The steady state binding of VTG was biphasic with respect to increasing ligand concentration, primarily due to a nonlinear receptor internalization rate as a function of occupancy. The nonlinear VTG binding was abolished by incubating the oocytes at 0 degree C. Our data are consistent with a model in which there is a cell surface regulatory component that facilitates the internalization of the occupied VTG receptor. Although both human chorionic gonadotropin and insulin stimulate VTG uptake by increasing the net rate of endocytosis, insulin also increases the association of the occupied VTG receptor with this regulatory component.
CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?

This article has been cited by other articles:

				W. Tong, R. Sulahian, A. W. Gross, N. Hendon, H. F. Lodish, and L. J.-s. Huang The Membrane-proximal Region of the Thrombopoietin Receptor Confers Its High Surface Expression by JAK2-dependent and -independent Mechanisms J. Biol. Chem., December 15, 2006; 281(50): 38930 - 38940. [Abstract] [Full Text] [PDF]

				T. W. Nordeng and O. Bakke Overexpression of Proteins Containing Tyrosine- or Leucine-based Sorting Signals Affects Transferrin Receptor Trafficking J. Biol. Chem., July 23, 1999; 274(30): 21139 - 21148. [Abstract] [Full Text] [PDF]

				C. R. Haft, M. de La Luz Sierra, I. Hamer, J.-L. Carpentier, and S. I. Taylor Analysis of the Juxtamembrane Dileucine Motif in the Insulin Receptor Endocrinology, April 1, 1998; 139(4): 1618 - 1629. [Abstract] [Full Text] [PDF]

				F Fagotto and F. Maxfield Changes in yolk platelet pH during Xenopus laevis development correlate with yolk utilization. A quantitative confocal microscopy study J. Cell Sci., January 12, 1994; 107(12): 3325 - 3337. [Abstract] [PDF]