Annexins expressed on the cell surface serve as receptors for adhesion to immobilized fetuin-A.
Fetuin-A is a major constituent of the fetal bovine serum used extensively in cell culture media. We hereby present data demonstrating that breast carcinoma cells can adhere to immobilized fetuin-A in a calcium-dependent fashion. Interestingly, the cells can also divide and attain confluency under these conditions. Using a proteomic approach, we have identified annexin-II and -VI as the putative cell surface receptors for fetuin-A in the presence of Ca2+ ions. Biotinylation of cell surface proteins followed by immunoprecipitation revealed that annexin-VI was expressed on the extracytoplasmic surface of the cell membranes. Finally, to demonstrate that annexin-II and -VI were the adhesive receptors for fetuin-A, siRNA knockdown of expression of the annexins significantly reduced the calcium-mediated adhesion. Interestingly, we demonstrated that the tumor cells could also adhere to immobilized fetuin-A in the presence of magnesium ions, and that this adhesion was most likely mediated by integrins because neutralizing antibodies against beta1 integrins substantially reduced the adhesion. Our studies suggest that the expression of annexin-II and -VI and possibly other members of the family mediate novel adhesion and signaling mechanisms in tumor cells.
Department of Biochemistry, Meharry Medical College, 1005 Dr. D.B. Todd Jr. Blvd. Nashville, TN 37208-3599, USA.
Madappa N
MN
Kundranda
Sanhita
S
Ray
Margaret
M
Saria
David
D
Friedman
Lynn M
LM
Matrisian
Pavel
P
Lukyanov
Josiah
J
Ochieng
D017306:Annexin A2 / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D017314:Annexin A4 / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D000906:Antibodies / Q000276:immunology / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology; D002448:Cell Adhesion / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000378:metabolism*; D024141:Collagen Type IV / Q000378:metabolism; D031541:Fluorescence Resonance Energy Transfer; D006801:Humans; D019012:Integrin beta1 / Q000276:immunology / Q000378:metabolism; D008274:Magnesium / Q000494:pharmacology; D011485:Protein Binding; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000378:metabolism; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D000509:alpha-Fetoproteins / Q000378:metabolism*
D017306:Annexin A2; D017314:Annexin A4; D000906:Antibodies; D024141:Collagen Type IV; D019012:Integrin beta1; D034741:RNA, Small Interfering; D011956:Receptors, Cell Surface; D000509:alpha-Fetoproteins; D008274:Magnesium; D002118:Calcium