The small GTPases Rab5a, Rab5b and Rab5c are differentially phosphorylated in vitro.
Rab GTPases play a fundamental role in the regulation of membrane traffic. Three different Rab5 isoforms have been reported but no differences in their function in endocytosis have been discovered. As the Rab5 isoforms show a conserved consensus site for Ser/Thr phosphorylation, we investigated whether this site was phosphorylated. Here, we report that the three Rab5 proteins are differentially recognized by different kinases. Rab5a is efficiently phosphorylated by extracellular-regulated kinase 1 but not by extracellular-regulated kinase 2, while cdc2 kinase preferentially phosphorylates Ser-123 of Rab5b. These findings strongly suggest that phosphorylation could be important to differentially regulate the function of the Rab5 isoforms.
Dipartimento di Biologia e Patologia Cellulare e Molecolare L. Califano and Centro di Endocrinologia ed Oncologia Sperimentale G. Salvatore del Consiglio Nazionale delle Ricerche, Napoli, Italy.
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Bucci
D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D020558:GTP Phosphohydrolases / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000378:metabolism*; D007527:Isoenzymes / Q000378:metabolism; D048031:JNK Mitogen-Activated Protein Kinases; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D010766:Phosphorylation; D013379:Substrate Specificity; D020696:rab5 GTP-Binding Proteins
D007527:Isoenzymes; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins; D020696:rab5 GTP-Binding Proteins