A prototypic platelet septin and its participation in secretion.
Studies are presented characterizing platelet CDCrel-1, a protein expressed to high levels by megakaryocytes and belonging to a family of conserved proteins, termed septin. Septin filaments originally were identified in yeast as essential for budding but have become increasingly associated with processes in higher eukaryotic cells involving active membrane movement such as cytokinesis and vesicle trafficking. Direct proof of an in vivo function for septins in higher eukaryotes is limited to the characterization of the Drosophila septin, termed PNUT. We present studies identifying platelet CDCrel-1 as a protein kinase substrate in the presence of known platelet agonists. The immunopurification of CDCrel-1 revealed it to be part of a macromolecular complex containing a protein involved in platelet secretion, syntaxin 4. Moreover, CDCrel-1 was localized in situ to areas surrounding platelet-storage granules. The relevance of CDCrel-1 to normal platelet function was established with the characterization of platelets from a CDCrel-1(Null) mouse. As compared with platelets from wild-type littermates, CDCrel-1(Null) platelets aggregate and release stored [14C]serotonin in the presence of subthreshold levels of collagen. These results provide new insights into the mechanisms regulating platelet secretion and identify platelet septins as a protein family contributing to membrane trafficking within the megakaryocyte and platelet.
Dent
Judith
J
Division of Experimental Hemostasis and Thrombosis, Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, CA 92037, USA.
Kato
Kazunobu
K
Peng
Xiao-Rong
XR
Martinez
Constantino
C
Cattaneo
Marco
M
Poujol
Christel
C
Nurden
Paquita
P
Nurden
Alan
A
Trimble
William S
WS
Ware
Jerry
J
D000595:Amino Acid Sequence; D000818:Animals; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism*; D018797:Cell Cycle Proteins; D003094:Collagen / Q000494:pharmacology; D006801:Humans; D017403:In Situ Hybridization; D051379:Mice; D018345:Mice, Knockout; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D058112:Septins; D017386:Sequence Homology, Amino Acid; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013917:Thrombin / Q000494:pharmacology
D018797:Cell Cycle Proteins; D009419:Nerve Tissue Proteins; D003094:Collagen; D013917:Thrombin; C109366:SEPTIN5 protein, human; C491612:Sept5 protein, mouse; D058112:Septins; D013755:Tetradecanoylphorbol Acetate