Biomedical subjects

J V Moyano

Publications and source records attributed to J V Moyano.

3 recordsLinked to original sources

PubMed2001

Interference of tenascin-C with syndecan-4 binding to fibronectin blocks cell adhesion and stimulates tumor cell proliferation.

Tenascin-C is an adhesion-modulatory extracellular matrix molecule that is highly expressed in tumors. To investigate the effect of tenascin-C on tumor cells, we analyzed its antiadhesive nature and effect on tumor cell proliferation in a fibronectin context. Glioblastoma and breast carcinoma cell adhesion was compromised by a mixed fibronectin/tenascin-C substratum, which concomitantly caused increased tumor-cell proliferation. We identified the antiadhesive mechanism as a specific interference of tenascin-C with cell binding to the HepII/syndecan-4 site in fibronectin through direct binding of tenascin-C to the 13th fibronectin type III repeat (FNIII13). Cell adhesion and proliferation levels were restored by the addition of FNIII13. Overexpression of syndecan-4, but not syndecan-1 or -2, reverted the cell adhesion defect of tenascin-C. We characterized FNIII13 as the binding site for syndecan-4. Thus we describe a novel mechanism by which tenascin-C impairs the adhesive function of fibronectin through binding to FNIII13, thereby inhibiting the coreceptor function of syndecan-4 in fibronectin-induced integrin signaling.

Animals↗

PubMed1999

Cooperative role for activated alpha4 beta1 integrin and chondroitin sulfate proteoglycans in cell adhesion to the heparin III domain of fibronectin. Identification of a novel heparin and cell binding sequence in repeat III5.

We recently reported that the heparin (Hep) III domain of fibronectin contains the H2 cell adhesion site in repeat III5 which binds activated alpha4 integrins. We have now further characterized the heparin and cell binding activities of this domain. A recombinant fragment containing repeats III4-III5 (FN-III4-5) induced Jurkat cell adhesion upon integrin activation with Mn2+ or TS2/16 monoclonal antibody (anti-beta1). Adhesion of Mn2+-treated cells to FN-III4-5 or FN-III5 fragments was inhibited by chondroitinase ABC and ACII but not by the anti-alpha4 monoclonal antibody HP2/1. In contrast, HP2/1 completely blocked adhesion of TS2/16-treated cells while chondroitinase had a partial (FN-III4-5) or minor (FN-III5) effect. Thus, the role of each receptor depended on the stimulus used to activate alpha4 beta1. The combination of HP2/1 and chondroitinase at dilutions which did not inhibit when used individually abolished adhesion of Mn2+ or TS2/16-treated cells to both fragments, indicating a cooperative effect between alpha4beta1 and chondroitin sulfate proteoglycans (CSPG). Furthermore, we have identified a 20-amino acid sequence in III5 (HBP/III5) which binds heparin and induces cell adhesion via CSPG exclusively. Although soluble HBP/III5 was a poor inhibitor, when combined with H2, it abolished adhesion to FN-III4-5 and FN-III5 fragments. These results establish that adhesion to the Hep III domain involves the cooperation of activated alpha4 beta1 and CSPG and show that HBP/III5 is a novel heparin and CSPG-binding site contributing to cell adhesion to this domain.

Amino Acid Sequence↗

PubMed1997

Fibronectin type III5 repeat contains a novel cell adhesion sequence, KLDAPT, which binds activated alpha4beta1 and alpha4beta7 integrins.

The region of fibronectin encompassing type III repeats 4-6 contains a low affinity heparin binding domain, but its physiological significance is not clear. We have studied whether this domain is able to interact with cells as already shown for other heparin binding domains of fibronectin. A computer search based on homologies with known active sites in fibronectin revealed the sequence KLDAPT located in FN-III5. A synthetic peptide containing this sequence induced lymphoid cell adhesion upon treatment with the activating anti-beta1 monoclonal antibody (mAb) TS2/16 or with Mn2+, indicating that KLDAPT was binding to an integrin. A recombinant fragment containing repeat III5 (FN-III5) also mediated adhesion of TS2/16/Mn2+-treated cells while the FN-III6 fragment did not. Soluble KLDAPT peptide inhibited cell adhesion to FN-III5 as well as to a 38-kDa fibronectin fragment and VCAM-1, two previously known ligands for alpha4beta1 integrin. KLDAPT also competed with the binding of soluble alkaline phosphatase-coupled VCAM-Ig to Mn2+-treated alpha4beta1. Furthermore, mAbs anti-alpha4 and anti-alpha4beta7, but not mAbs to other integrins, inhibited cell adhesion to FN-III5 and KLDAPT. These results therefore establish a cell adhesive function for the FN-III5 repeat and show that KLDAPT is a novel fibronectin ligand for activated alpha4 integrins.

Amino Acid Sequence↗