A-RAF kinase functions in ARF6 regulated endocytic membrane traffic.
BACKGROUND
RAF kinases direct ERK MAPK signaling to distinct subcellular compartments in response to growth factor stimulation.


RESULTS
Of the three mammalian isoforms A-RAF is special in that one of its two lipid binding domains mediates a unique pattern of membrane localization. Specific membrane binding is retained by an N-terminal fragment (AR149) that corresponds to a naturally occurring splice variant termed DA-RAF2. AR149 colocalizes with ARF6 on tubular endosomes and has a dominant negative effect on endocytic trafficking. Moreover actin polymerization of yeast and mammalian cells is abolished. AR149/DA-RAF2 does not affect the internalization step of endocytosis, but trafficking to the recycling compartment.


CONCLUSIONS
A-RAF induced ERK activation is required for this step by activating ARF6, as A-RAF depletion or inhibition of the A-RAF controlled MEK-ERK cascade blocks recycling. These data led to a new model for A-RAF function in endocytic trafficking.
Nekhoroshkova
Elena
E
Institut für Medizinische Strahlenkunde und Zellforschung, University of Würzburg, Würzburg, Germany.
Albert
Stefan
S
Becker
Matthias
M
Rapp
Ulf R
UR
D000089982:ADP-Ribosylation Factor 6; D020727:ADP-Ribosylation Factors / Q000502:physiology*; D000818:Animals; D002460:Cell Line; D002462:Cell Membrane / Q000201:enzymology / Q000378:metabolism; D004705:Endocytosis / Q000502:physiology*; D004789:Enzyme Activation; D019084:Fluorescent Antibody Technique, Indirect; D006801:Humans; D008856:Microscopy, Fluorescence; D048491:Proto-Oncogene Proteins A-raf / Q000378:metabolism*; D034741:RNA, Small Interfering
D000089982:ADP-Ribosylation Factor 6; D034741:RNA, Small Interfering; D048491:Proto-Oncogene Proteins A-raf; D020727:ADP-Ribosylation Factors; C000715348:ARF6 protein, human