Peptide G, containing the binding site of the 67-kDa laminin receptor, increases and stabilizes laminin binding to cancer cells.
We investigated the effect of peptide G, a synthetic peptide derived from the sequence of the 37-kDa laminin receptor precursor, on the interaction of laminin in two tumor cell lines one of which produces laminin and one of which does not. Addition of peptide G to the culture medium induced a significant increase in the amount of endogenous laminin detectable on the cell membrane of both cell lines. Moreover, pretreatment of exogenous laminin with peptide G dramatically increased laminin binding on both cell lines. Kinetics analysis of membrane-bound labeled laminin revealed a 3-fold decrease in the kd of peptide G-treated laminin compared with untreated or unrelated or scrambled peptide-treated laminin. Moreover, the affinity constant of peptide G-treated laminin increased 2-fold, with a doubling of the number of laminin binding sites, as determined by Scatchard analysis. Expression of the VLA6 integrin receptor on the cell membrane increased after incubation with peptide G-treated laminin. However, the lower binding inhibition of peptide G-treated laminin after anti-VLA6 antibody or cation chelation treatment indicates that membrane molecules in addition to integrin receptors are involved in the recognition of peptide G-modified laminin. These "new" laminin-binding proteins also mediated cell adhesion to laminin, the first step in tumor invasion. Together, the data suggest that peptide G increases and stabilizes laminin binding on tumor cells, involving surface receptors that normally do not take part in this interaction. This might explain the abundant clinical and experimental data suggesting a key role for the 67-kDa laminin receptor in the interaction between cancer cells and the basement membrane glycoprotein laminin during tumor invasion and metastasis.
Magnifico
A
A
Division of Experimental Oncology E, Istituto Nazionale Tumori, Via Venezian 1, 20133 Milan, Italy.
Tagliabue
E
E
Butó
S
S
Ardini
E
E
Castronovo
V
V
Colnaghi
M I
MI
Ménard
S
S
D002448:Cell Adhesion; D006801:Humans; D007700:Kinetics; D007797:Laminin / Q000378:metabolism*; D009369:Neoplasms / Q000378:metabolism*; D011498:Protein Precursors; D017474:Receptors, Laminin / Q000378:metabolism*; D014407:Tumor Cells, Cultured
D007797:Laminin; D011498:Protein Precursors; D017474:Receptors, Laminin