Prominin-2 is a cholesterol-binding protein associated with apical and basolateral plasmalemmal protrusions in polarized epithelial cells and released into urine

Cell Tissue Res. 2007 Apr;328(1):31-47. doi: 10.1007/s00441-006-0324-z. Epub 2006 Nov 16.

Abstract

Prominin-2 is a pentaspan membrane glycoprotein structurally related to the cholesterol-binding protein prominin-1, which is expressed in epithelial and non-epithelial cells. Although prominin-1 expression is widespread throughout the organism, the loss of its function solely causes retinal degeneration. The finding that prominin-2 appears to be restricted to epithelial cells, such as those found in kidney tubules, raises the possibility that prominin-2 functionally substitutes prominin-1 in tissues other than the retina and provokes a search for a definition of its morphological and biochemical characteristics. Here, we have investigated, by using MDCK cells as an epithelial cell model, whether prominin-2 shares the biochemical and morphological properties of prominin-1. Interestingly, we have found that, whereas prominin-2 is not restricted to the apical domain like prominin-1 but is distributed in a non-polarized fashion between the apical and basolateral plasma membranes, it retains the main feature of prominin-1, i.e. its selective concentration in plasmalemmal protrusions; prominin-2 is confined to microvilli, cilia and other acetylated tubulin-positive protruding structures. Similar to prominin-1, prominin-2 is partly associated with detergent-resistant membranes in a cholesterol-dependent manner, suggesting its incorporation into membrane microdomains, and binds directly to plasma membrane cholesterol. Finally, prominin-2 is also associated with small membrane particles that are released into the culture media and found in a physiological fluid, i.e. urine. Together, these data show that all the characteristics of prominin-1 are shared by prominin-2, which is in agreement with a possible redundancy in their role as potential organizers of plasma membrane protrusions.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Carrier Proteins / urine*
  • Cell Line
  • Cell Membrane / drug effects
  • Cell Membrane / ultrastructure
  • Cell Polarity* / drug effects
  • Cell Surface Extensions / drug effects
  • Cell Surface Extensions / metabolism*
  • Cholesterol / deficiency
  • Detergents / pharmacology
  • Epithelial Cells / cytology*
  • Epithelial Cells / drug effects
  • Membrane Glycoproteins / urine*
  • Pancreatic Elastase
  • Polyethylene Glycols / pharmacology
  • Recombinant Fusion Proteins / metabolism

Substances

  • Carrier Proteins
  • Detergents
  • Membrane Glycoproteins
  • Prom2 protein, mouse
  • Prom2 protein, rat
  • Recombinant Fusion Proteins
  • Lubrol WX
  • Polyethylene Glycols
  • Cholesterol
  • Pancreatic Elastase
  • cholesterol-binding protein