alpha6beta1-Integrin, a major cell surface carrier of beta1-6-branched oligosaccharides, mediates migration of EJ-ras-transformed fibroblasts on laminin-1 independently of its glycosylation state.
EJ-ras oncogene-induced malignant transformation is characterized by a series of changes in cell surface carbohydrates and cell-cell and cell-matrix interactions. Here, we show that EJ-ras-transformed NIH-3T3 fibroblasts acquired a migratory phenotype on laminin-1 surfaces. Such a phenotype was accompanied by overexpression of: (a) functional alpha6beta1, but not other laminin binding beta1-integrins; and (b) glycoconjugates on the cell surface bearing large oligosaccharides recognized by leukoagglutinin from Phaseolus vulgaris (L-PHA). The internal pool of pre-beta1-integrins was differently regulated in EJ-ras-transformed cells compared with nontransfected fibroblasts. Conversion of pre-beta1- into mature beta1-integrins was faster in EJ-ras-transformed cells, a process associated with the overexpression of the alpha6-chain. Overexpression of L-PHA-reactive oligosaccharides is dependent on the activity of N-acetylglucosaminyltransferase V, which is increased in transformed cells [J. W. Dennis et al., Science (Washington DC), 236: 582-585, 1987]. We show that beta1-integrins were the major carriers of L-PHA-reactive oligosaccharides on the cell surface. This glycosylation pattern, however, was not necessary for either the cell surface expression of beta1-integrins or their functional activity in the migratory response to laminin-1. Moreover, EJ-ras-transformed fibroblasts aggregated spontaneously. These effects were not observed in c-jun-transfected fibroblasts, which were unable to migrate on laminin, did not overexpress either beta1-integrins or L-PHA-reactive oligosaccharides, and did not self-aggregate.
Jasiulionis
M G
MG
Ludwig Institute for Cancer Research, Sao Paulo, Brasil.
Chammas
R
R
Ventura
A M
AM
Travassos
L R
LR
Brentani
R R
RR
D016475:3T3 Cells; D000818:Animals; D002461:Cell Line, Transformed; D002465:Cell Movement; D002471:Cell Transformation, Neoplastic / Q000378:metabolism; D005260:Female; D011905:Genes, ras; D006031:Glycosylation; D039121:Integrin alpha6beta1; D019012:Integrin beta1 / Q000378:metabolism*; D016023:Integrins / Q000502:physiology*; D007797:Laminin / Q000502:physiology*; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D009844:Oligosaccharides / Q000378:metabolism*; D010835:Phytohemagglutinins / Q000378:metabolism
D039121:Integrin alpha6beta1; D019012:Integrin beta1; D016023:Integrins; D007797:Laminin; D009844:Oligosaccharides; D010835:Phytohemagglutinins; C100156:leukoagglutinins, plants