cDNA cloning and molecular characterization of MSE55, a novel human serum constituent protein that displays bone marrow stromal/endothelial cell-specific expression.
Hemonectin is a lineage-specific cytoadhesive protein that may be involved in the developmentally regulated adhesion of granulocytic cells to bone marrow stroma. Immunoblot analysis using an anti-hemonectin antibody recognizes two distinct immunoreactive species in endothelial cell lysates (approximately M(r) 65,000) and human serum (approximately M(r) 55,000). Initial characterization of the 55-kDa protein has now been completed by isolating the cDNA from a human endothelial cell expression library. Sequence analysis of overlapping clones identifies a composite sequence spanning 2030 nucleotides with an open reading frame of 1173 base pairs. No significant sequence similarity was observed on analysis of current GenBank databases. The open reading frame was expressed as a recombinant protein in Escherichia coli and used as an immunogen for the production of a specific polyclonal antibody. Immunoblotting with this antibody identifies a single immunoreactive species of apparent M(r) 55,000 in HUVEC lysates and human serum, confirming that a secreted form normally circulates as a serum constituent protein. This antibody fails to recognize purified hemonectin, suggesting that the M(r) 55,000 protein is not hemonectin. Cross-species Southern blot analysis reveals persistent hybridizing fragments in all species tested, suggestive of a developmentally conserved function. Northern blot analysis demonstrates expression limited to endothelial and bone marrow stromal cells, but not poly(A) RNA from monkey liver, spleen, brain, lung, and kidney. On this basis, we have designated this novel protein MSE55, for marrow stromal/endothelial cell protein with a molecular mass of 55,000 daltons. Its tissue-specific expression may suggest a functional role in hematopoiesis.
Bahou
W F
WF
Division of Hematology, State University of New York, Stony Brook 11794-8151.
Campbell
A D
AD
Wicha
M S
MS
D048868:Adaptor Proteins, Signal Transducing; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001798:Blood Proteins / Q000235:genetics* / Q000302:isolation & purification; D015139:Blotting, Southern; D001853:Bone Marrow / Q000502:physiology*; D002352:Carrier Proteins; D002478:Cells, Cultured; D002999:Clone Cells; D003001:Cloning, Molecular; D003598:Cytoskeletal Proteins; D004247:DNA / Q000235:genetics* / Q000302:isolation & purification; D004730:Endothelium, Vascular / Q000502:physiology*; D020549:GTP Phosphohydrolase Activators; D020558:GTP Phosphohydrolases; D020555:GTP-Binding Protein Regulators; D015723:Gene Library; D006801:Humans; D015151:Immunoblotting; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides; D014176:Protein Biosynthesis; D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins / Q000302:isolation & purification; D015183:Restriction Mapping; D013045:Species Specificity; D014471:Umbilical Veins; D020764:cdc42 GTP-Binding Protein; D020741:rho GTP-Binding Proteins
D048868:Adaptor Proteins, Signal Transducing; D001798:Blood Proteins; C422984:CDC42EP2 protein, human; C484093:CDC42EP3 protein, human; C422985:CDC42EP4 protein, human; C484094:CDC42EP5 protein, human; D002352:Carrier Proteins; D003598:Cytoskeletal Proteins; D020549:GTP Phosphohydrolase Activators; D020555:GTP-Binding Protein Regulators; D009838:Oligodeoxyribonucleotides; D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins; C075598:CDC42EP1 protein, human; D004247:DNA; D020558:GTP Phosphohydrolases; D020764:cdc42 GTP-Binding Protein; D020741:rho GTP-Binding Proteins