Rab8 promotes polarized membrane transport through reorganization of actin and microtubules in fibroblasts.
Rab8 is a small Ras-like GTPase that regulates polarized membrane transport to the basolateral membrane in epithelial cells and to the dendrites in neurons. It has recently been demonstrated that fibroblasts sort newly synthesized proteins into two different pathways for delivery to the cell surface that are equivalent to the apical and the basolateral post-Golgi routes in epithelial cells (Yoshimori, T., P. Keller, M.G. Roth, and K. Simons. 1996. J. Cell Biol. 133:247-256). To determine the role of Rab8 in fibroblasts, we used both transient expression systems and stable cell lines expressing mutant or wild-type (wt) Rab8. A dramatic change in cell morphology occurred in BHK cells expressing both the wt Rab8 and the activated form of the GTPase, the Rab8Q67L mutant. These cells formed processes as a result of a reorganization of both their actin filaments and microtubules. Newly synthesized vesicular stomatitis virus G glycoprotein, a basolateral marker protein in MDCK cells, was preferentially delivered into these cell outgrowths. Based on these findings, we propose that Rab8 provides a link between the machinery responsible for the formation of cell protrusions and polarized biosynthetic membrane traffic.
Peränen
J
J
European Molecular Biology Laboratory, Cell Biology Programme, Heidelberg, Germany.
Auvinen
P
P
Virta
H
H
Wepf
R
R
Simons
K
K
D008841:Actin Cytoskeleton / Q000378:metabolism; D000199:Actins / Q000378:metabolism*; D000818:Animals; D001692:Biological Transport; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism*; D016764:Cell Polarity; D048429:Cell Size / Q000502:physiology; D006224:Cricetinae; D005347:Fibroblasts / Q000166:cytology* / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000235:genetics / Q000502:physiology*; D015870:Gene Expression; D006056:Golgi Apparatus; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000235:genetics / Q000378:metabolism; D007668:Kidney; D008562:Membrane Glycoproteins; D008870:Microtubules / Q000378:metabolism*; D017354:Point Mutation; D011993:Recombinant Fusion Proteins; D014759:Viral Envelope Proteins / Q000235:genetics / Q000378:metabolism; D020691:rab GTP-Binding Proteins
D000199:Actins; C028391:G protein, vesicular stomatitis virus; D019267:Hemagglutinin Glycoproteins, Influenza Virus; D008562:Membrane Glycoproteins; D011993:Recombinant Fusion Proteins; D014759:Viral Envelope Proteins; D019204:GTP-Binding Proteins; D020691:rab GTP-Binding Proteins