Colocalization of the p185HER2 oncoprotein and integrin alpha 6 beta 4 in Calu-3 lung carcinoma cells.
Anti-p185HER2 monoclonal antibodies often show intense reactivity with the basement membrane of tumor cells that overexpress the HER2/neu gene product (p185HER2). To evaluate a possible interaction between p185HER2 and adhesion molecules or their receptors, the polarity of p185HER2 was tested in lung carcinoma cell line Calu-3, which overexpresses this protein, in cultures grown as confluent monolayers or as aggregates. MAb immunostaining patterns indicated that p185HER2 is concentrated on the baso-lateral membrane of cells and that it colocalizes with the integrin alpha 6 beta 4 at the cell-cell junctions where laminin is also found. The same membrane region showed intense reactivity with antiphosphotyrosine antibodies. Furthermore, integrin clustering induced by the specific antibody was accompanied by the clustering of p185HER2, as indicated by immunoelectron microscopy, and by a subsequent increase in p185HER2 tyrosine phosphorylation. Treatment with exogenous laminin also resulted in increased basal levels of p185HER2 phosphorylation. These data suggest a physical interaction between the integrin and the oncoprotein that might be functionally relevant in directly controlling the tyrosine phosphorylation of the catalytic domain of p185HER2.
Division of Experimental Oncology, Istituto Nazionale Tumori, Milan, Italy.
M
M
Campiglio
E
E
Tagliabue
U
U
Srinivas
R
R
Pellegrini
S
S
Martignone
S
S
Ménard
M I
MI
Colnaghi
L
L
Lombardi
P C
PC
Marchisio
D000911:Antibodies, Monoclonal; D000954:Antigens, Surface / Q000032:analysis* / Q000378:metabolism; D014408:Biomarkers, Tumor / Q000032:analysis; D002460:Cell Line; D002462:Cell Membrane / Q000648:ultrastructure; D006801:Humans; D039161:Integrin alpha6beta4; D016023:Integrins / Q000032:analysis* / Q000378:metabolism; D008175:Lung Neoplasms / Q000378:metabolism / Q000473:pathology* / Q000648:ultrastructure; D008856:Microscopy, Fluorescence; D016253:Microscopy, Immunoelectron; D011863:Radioimmunoassay; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000032:analysis* / Q000378:metabolism; D014407:Tumor Cells, Cultured
D000911:Antibodies, Monoclonal; D000954:Antigens, Surface; D014408:Biomarkers, Tumor; D039161:Integrin alpha6beta4; D016023:Integrins; D018719:Erb-b2 Receptor Tyrosine Kinases