Interaction of calmodulin with the cytoplasmic domain of platelet glycoprotein VI.
The platelet collagen receptor, glycoprotein VI (GPVI), and GPIb-IX-V, which binds von Willebrand factor, initiate platelet aggregation at low or high shear stress, respectively. We recently reported that positively charged, membrane-proximal sequences within cytoplasmic domains of GPIbbeta and GPV of GPIb-IX-V bind calmodulin. We now show that GPVI also binds calmodulin as follows-(1) calmodulin coimmunoprecipitated with GPVI from resting platelet lysates using an anti-GPVI IgG, but partially dissociated in platelets activated by collagen or collagen-related peptide; (2) calmodulin coprecipitated from platelet lysates with maltose-binding protein (MBP)-GPVI cytoplasmic domain fusion protein, but not MBP alone; (3) GPVI-related synthetic peptide based on the membrane-proximal sequence, His269-Pro287, induced a shift in calmodulin migration on nondenaturing gels, an assay that identifies calmodulin-binding peptides. His269-Pro287 is analogous to the calmodulin-binding sequence in GPIbbeta. The novel interaction of GPVI and calmodulin may regulate aspects of GPVI function.
Andrews
Robert K
RK
Hazel and Pip Appel Vascular Biology Laboratory, Baker Medical Research Institute, Melbourne, Australia. rkandrews@hotmail.com
Suzuki-Inoue
Katsue
K
Shen
Yang
Y
Tulasne
David
D
Watson
Stephen P
SP
Berndt
Michael C
MC
D000595:Amino Acid Sequence; D001665:Binding Sites; D001792:Blood Platelets / Q000378:metabolism*; D002147:Calmodulin / Q000097:blood*; D002352:Carrier Proteins / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D006801:Humans; D058619:Maltose-Binding Proteins; D008969:Molecular Sequence Data; D019038:Platelet Glycoprotein GPIb-IX Complex / Q000737:chemistry / Q000378:metabolism*; D010980:Platelet Membrane Glycoproteins / Q000737:chemistry / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
D002147:Calmodulin; D002352:Carrier Proteins; D058619:Maltose-Binding Proteins; D019038:Platelet Glycoprotein GPIb-IX Complex; D010980:Platelet Membrane Glycoproteins; D011993:Recombinant Fusion Proteins; C032193:glycoprotein receptor GPIb-IX; C098341:platelet membrane glycoprotein VI