Ubiquitination and Lipid Rafts in Erythropoietin Receptor Internalization and Signaling

Abstract

Signaling through the erythropoietin receptor (EpoR) is important in the proliferation and differentiation of red blood cells and their precursors. Many of the molecular details of this signaling pathway have been described. In these experiments, we endeavored to more fully map the determinants of EpoR signaling by addressing the importance of membrane cholesterol and the possible participation of membrane lipid rafts. The results of our experiments show that depletion of cholesterol from the surface of Ba/F3 cells stably expressing the receptor results in decreased STAT5 activation. Tagged EpoR can be detected within the lighter fractions of a density gradient cellular fractionation, suggesting that the receptor may co‐localize with membrane lipid rafts. Interestingly, cells expressing a modified EpoR lacking intracellular domain lysine residues were seemingly unaffected by the pharmacologic agent methyl‐β‐cyclodextrin. The significance and mechanism of this are unknown, but point to the possibility that receptor ubiquitination may be involved in receptor localization and/or migration to lipid rafts.