Analysis of CD36 binding domains: ligand specificity controlled by dephosphorylation of an ectodomain.
The protein CD36 is a membrane receptor for thrombospondin (TSP), malaria-infected erythrocytes, and collagen. Three functional sequences were identified within a single disulfide loop of CD36: one that mediates TSP binding (amino acids 87 to 99) and two that support malarial cytoadhesion (amino acids 8 to 21 and 97 to 110). One of these peptides (p87-99) is a consensus protein kinase C (PKC) phosphorylation site. Dephosphorylation of constitutively phosphorylated CD36 in resting platelets and a megakaryocytic cell line led to the loss of collagen adhesion and platelet reactivity to collagen, with a reciprocal increase in TSP binding. PKC-mediated phosphorylation of this ectodomain resulted in a loss of TSP binding and the reciprocal acquisition of collagen binding. In site-directed mutagenesis studies, when the threonine phosphorylation site was changed to alanine, CD36 was expressed in a dephosphorylated state and bound to TSP constitutively.
Asch
A S
AS
Division of Hematology-Oncology, Cornell University Medical College, New York, NY 10021.
Liu
I
I
Briccetti
F M
FM
Barnwell
J W
JW
Kwakye-Berko
F
F
Dokun
A
A
Goldberger
J
J
Pernambuco
M
M
D000595:Amino Acid Sequence; D000818:Animals; D015703:Antigens, CD / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D001792:Blood Platelets / Q000378:metabolism*; D018955:CD36 Antigens; D002448:Cell Adhesion; D002460:Cell Line; D003094:Collagen / Q000378:metabolism*; D004912:Erythrocytes / Q000166:cytology / Q000469:parasitology; D006801:Humans; D008533:Megakaryocytes / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000378:metabolism*; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010766:Phosphorylation; D010963:Plasmodium falciparum / Q000502:physiology; D010973:Platelet Adhesiveness; D010974:Platelet Aggregation; D010980:Platelet Membrane Glycoproteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011493:Protein Kinase C / Q000378:metabolism; D016024:Receptors, Cytoadhesin / Q000378:metabolism; D019699:Thrombospondins
D015703:Antigens, CD; D018955:CD36 Antigens; D008562:Membrane Glycoproteins; D010980:Platelet Membrane Glycoproteins; D016024:Receptors, Cytoadhesin; D019699:Thrombospondins; D003094:Collagen; D011493:Protein Kinase C