The phosphatidylinositol 4-kinase PI4KIIIalpha is required for the recruitment of GBF1 to Golgi membranes.
Sorting from the Golgi apparatus requires the recruitment of cytosolic coat proteins to package cargo into trafficking vesicles. An important early step in the formation of trafficking vesicles is the activation of Arf1 by the guanine nucleotide exchange factor GBF1. To activate Arf1, GBF1 must be recruited to and bound to Golgi membranes, a process that requires Rab1b. However, the mechanistic details of how Rab1 is implicated in GBF1 recruitment are not known. In this study, we demonstrate that the recruitment of GBF1 also requires phosphatidylinositol 4-phosphate [PtdIns(4)P]. Inhibitors of PtdIns(4)P synthesis or depletion of PI4KIIIalpha, a phosphatidylinositol 4-kinase localized to the endoplasmic reticulum and Golgi, prevents the recruitment of GBF1 to Golgi membranes. Interestingly, transfection of dominant-active Rab1 increased the amount of PtdIns(4)P at the Golgi, as detected by GFP-PH, a PtdIns(4)P-sensing probe. We propose that Rab1 contributes to the specificity and timing of GBF1 recruitment by activating PI4KIIIalpha. The PtdIns(4)P produced then allows GBF1 to bind to Golgi membranes and activate Arf1.
Centre de Recherche de l'Hôpital Maisonneuve-Rosemont et Département de Médecine, Université de Montréal, Montréal, Québec H1T 2M4, Canada.
Karine
K
Dumaresq-Doiron
Marie-France
MF
Savard
Salima
S
Akam
Santiago
S
Costantino
Stephane
S
Lefrancois
D019870:1-Phosphatidylinositol 4-Kinase / Q000235:genetics / Q000378:metabolism*; D020823:ADP-Ribosylation Factor 1 / Q000378:metabolism; D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D004791:Enzyme Inhibitors / Q000378:metabolism; D006056:Golgi Apparatus / Q000378:metabolism / Q000648:ultrastructure*; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D007425:Intracellular Membranes / Q000378:metabolism*; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism*; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism; D034622:RNA Interference; D020761:rab1 GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism
D004791:Enzyme Inhibitors; C120445:GBF1 protein, human; D020662:Guanine Nucleotide Exchange Factors; D007527:Isoenzymes; D018129:Phosphatidylinositol Phosphates; C037178:phosphatidylinositol 4-phosphate; D019870:1-Phosphatidylinositol 4-Kinase; C000618292:PI4KIIIalpha protein, human; D020823:ADP-Ribosylation Factor 1; D020761:rab1 GTP-Binding Proteins