Endomembrane trafficking of ras: the CAAX motif targets proteins to the ER and Golgi.
We show that Nras is transiently localized in the Golgi prior to the plasma membrane (PM). Moreover, green fluorescent protein (GFP)-tagged Nras illuminated motile, peri-Golgi vesicles, and prolonged BFA treatment blocked PM expression. GFP-Hras colocalized with GFP-Nras, but GFP-Kras4B revealed less Golgi and no vesicular fluorescence. Whereas a secondary membrane targeting signal was required for PM expression, the CAAX motif alone was necessary and sufficient to target proteins to the endomembrane where they were methylated, a modification required for efficient membrane association. Thus, prenylated CAAX proteins do not associate directly with the PM but instead associate with the endomembrane and are subsequently transported to the PM, a process that requires a secondary targeting motif.
Department of Medicine, New York University School of Medicine, New York 10016, USA.
E
E
Choy
V K
VK
Chiu
J
J
Silletti
M
M
Feoktistov
T
T
Morimoto
D
D
Michaelson
I E
IE
Ivanov
M R
MR
Philips
D000595:Amino Acid Sequence; D000818:Animals; D016466:CHO Cells; D019556:COS Cells; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism*; D006224:Cricetinae; D004285:Dogs; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D006056:Golgi Apparatus / Q000378:metabolism*; D049452:Green Fluorescent Proteins; D007668:Kidney; D007700:Kinetics; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D014162:Transfection; D018631:ras Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
D008164:Luminescent Proteins; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; D018631:ras Proteins