Identification of the alpha IIb beta 3 integrin in murine tumor cells.
Previously, we have identified an alpha IIb beta 3-like integrin in tumor cells by using antibodies against platelet alpha IIb beta 3. However, alpha IIb beta 3 was considered to be expressed strictly in megakaryocyte lineage cells. In order to resolve this controversy, the alpha IIb beta 3-like integrin in murine B16 amelanotic melanoma (B16a) cells was characterized at DNA, RNA, and protein levels. The presence of alpha 5, alpha v, alpha IIb, beta 1, and beta 3 genes in B16a cells was confirmed by Southern analysis. mRNAs for all these integrins except alpha v were detectable by Northern blotting. The alpha IIb beta 3 protein was identified by Western blotting using subunit-specific antibodies and by immunoprecipitation using complex-specific antibody. The alpha IIb beta 3 integrin was localized intracellularly by immunocytochemistry. Finally, alpha IIb and beta 3 mRNAs were amplified by reverse transcription-polymerase chain reaction and the identity of alpha IIb was verified by sequencing. Partial DNA and deduced amino acid sequence analysis showed that B16a alpha IIb shares approximately 80% homology with the human alpha IIb and approximately 90% homology with the rat alpha IIb, whereas B16a alpha IIb shares only approximately 26% homology with the human alpha v. These experiments indicate that the alpha IIb beta 3-like protein in B16a cells is the authentic alpha IIb beta 3 and demonstrate, for the first time, that integrin alpha IIb beta 3 is not confined to megakaryocyte lineage cells.
Chen
Y Q
YQ
Department of Radiation Oncology, Wayne State University, Detroit, Michigan 48202.
Gao
X
X
Timar
J
J
Tang
D
D
Grossi
I M
IM
Chelladurai
M
M
Kunicki
T J
TJ
Fligiel
S E
SE
Taylor
J D
JD
Honn
K V
KV
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001792:Blood Platelets / Q000502:physiology*; D015153:Blotting, Western; D015342:DNA Probes; D006801:Humans; D016023:Integrins / Q000032:analysis* / Q000235:genetics*; D046911:Macromolecular Substances; D008546:Melanoma, Experimental / Q000235:genetics / Q000648:ultrastructure; D051379:Mice; D016253:Microscopy, Immunoelectron; D008969:Molecular Sequence Data; D012689:Sequence Homology, Nucleic Acid; D014407:Tumor Cells, Cultured
D015342:DNA Probes; D016023:Integrins; D046911:Macromolecular Substances