Rab3B in human platelet is membrane bound and interacts with Ca(2+)/calmodulin.
The subcellular distribution of Rab3B in fresh and aged platelets was determined and majority of the protein was localized with the particulate fraction with only a minor amount detected in the cytosol. Rab3B was pulled out from platelet particulate fraction with GST-RabGDI-alpha fusion protein. Using GST-Rab3B in in vitro pull-down experiments, the binding of calmodulin from platelet cytosol to Rab3B was demonstrated. In the reverse experiment, binding of Rab3B from platelet particulate and cytosolic fractions to Sepharose-CaM beads was also observed. The interaction between Rab3B and calmodulin was Ca(2+)-dependent but independent of the guanine nucleotide status of Rab3B. These findings provide evidence that Rab3B is primarily localized with the particulate fraction and that Ca(2+)/calmodulin could regulate function of this GTPase in the platelet.
Sidhu
R S
RS
Department of Oral Biology, University of Manitoba, Winnipeg, Manitoba, R3E 0W2, Canada.
Bhullar
R P
RP
D001792:Blood Platelets / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D002147:Calmodulin / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D020730:Guanine Nucleotide Dissociation Inhibitors / Q000378:metabolism; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism; D006153:Guanosine Diphosphate / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D008566:Membranes / Q000378:metabolism; D011485:Protein Binding; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013347:Subcellular Fractions / Q000378:metabolism; D020692:rab3 GTP-Binding Proteins / Q000097:blood*
D002147:Calmodulin; C086796:GDP dissociation inhibitor 1; D020730:Guanine Nucleotide Dissociation Inhibitors; D011993:Recombinant Fusion Proteins; D006153:Guanosine Diphosphate; D016244:Guanosine 5'-O-(3-Thiotriphosphate); C492131:RAB3B protein, human; D020692:rab3 GTP-Binding Proteins; D002118:Calcium