Prominin-2 is a cholesterol-binding protein associated with apical and basolateral plasmalemmal protrusions in polarized epithelial cells and released into urine.
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.
Florek
Mareike
M
Medical Clinic and Polyclinic I, Technische Universität Dresden, Fetscherstrasse 74, 01307 Dresden, Germany.
Bauer
Nicola
N
Janich
Peggy
P
Wilsch-Braeuninger
Michaela
M
Fargeas
Christine A
CA
Marzesco
Anne-Marie
AM
Ehninger
Gerhard
G
Thiele
Christoph
C
Huttner
Wieland B
WB
Corbeil
Denis
D
D000818:Animals; D002352:Carrier Proteins / Q000652:urine*; D002460:Cell Line; D002462:Cell Membrane / Q000187:drug effects / Q000648:ultrastructure; D016764:Cell Polarity / Q000187:drug effects; D022081:Cell Surface Extensions / Q000187:drug effects / Q000378:metabolism*; D002784:Cholesterol / Q000172:deficiency; D003902:Detergents / Q000494:pharmacology; D004847:Epithelial Cells / Q000166:cytology* / Q000187:drug effects; D008562:Membrane Glycoproteins / Q000652:urine*; D010196:Pancreatic Elastase; D011092:Polyethylene Glycols / Q000494:pharmacology; D011993:Recombinant Fusion Proteins / Q000378:metabolism
D002352:Carrier Proteins; D003902:Detergents; D008562:Membrane Glycoproteins; C473220:Prom2 protein, mouse; C473221:Prom2 protein, rat; D011993:Recombinant Fusion Proteins; C017474:Lubrol WX; D011092:Polyethylene Glycols; D002784:Cholesterol; D010196:Pancreatic Elastase; C017130:cholesterol-binding protein