Characterization of cell surface-expressed proteochondroitin sulfate of pre-B Nalm-6 cells and its possible role in laminin adhesion.
Cell surface-expressed proteoglycans mediate contacts to extracellular matrix (ECM). Human B lymphocytes produce a species of a proteochondroitin sulfate (CSPG) with an approximate molecular mass of 135-150 kDa. Using a monoclonal antibody (mAb) against B cell CSPG in flow cytometry we found that this CSPG is expressed on tumor cells of patients with CD19+ common acute lymphoblastic leukemia and on the corresponding cell lines Nalm-6, Reh and KM3. The CSPG is also present on hairy cell leukemia JOK-1 cells and weakly on the myeloma line U266. Concomitant with CSPG expression, Nalm-6 cells express the integrins alpha 5/beta 1 (CD49e/CD29) and alpha 6/beta 1 (CD49f/CD29), adhesion receptors for fibronectin and laminin, in contrast to the other two cell lines tested. Expression patterns of these adhesion receptors and CSPG were paralleled by strong adhesion of Nalm-6 to fibronectin and laminin. Adhesion of Nalm-6 to fibronectin was inhibited by the alpha 5-specific antibody SAM 1 by 80% whereas the alpha 6-specific antibody GoH3 reduced binding to laminin only by 20%. A possible involvement of surface-expressed CSPG in adhesion to ECM components was investigated by 24 h incubation of Nalm-6 cells with p-nitrophenyl-beta-D-xyloside, an inhibitor of proteoglycan glycosylation. By this treatment, both adhesion of Nalm-6 to laminin and expression of CSPG were reduced by 40-50%. Furthermore, addition of chondroitin-6-sulfate, a structural element of Nalm-6 CSPG, reduced adhesion of Nalm-6 to laminin by 60%. Chondroitin-4-sulfate, heparin and heparan sulfate did not effectively inhibit the adhesion process. These observations suggest that surface-expressed CSPG may be involved in binding of Nalm-6 cells to laminin and that the specific sulfation pattern of chondroitin-6-sulfate may be essential in this regard.
Blase
L
L
Tumor Immunology Program, German Cancer Research Center, Heidelberg, Germany.
Merling
A
A
Engelmann
S
S
Möller
P
P
Schwartz-Albiez
R
R
D015703:Antigens, CD / Q000378:metabolism; D002448:Cell Adhesion; D002462:Cell Membrane / Q000276:immunology / Q000378:metabolism; D011508:Chondroitin Sulfate Proteoglycans / Q000378:metabolism*; D005353:Fibronectins / Q000378:metabolism; D006801:Humans; D039482:Integrin alpha5; D039503:Integrin alpha6; D039121:Integrin alpha6beta1; D019012:Integrin beta1 / Q000378:metabolism; D016023:Integrins / Q000378:metabolism; D007797:Laminin / Q000378:metabolism*; D015452:Precursor B-Cell Lymphoblastic Leukemia-Lymphoma / Q000276:immunology / Q000378:metabolism* / Q000473:pathology; D017469:Receptors, Fibronectin / Q000378:metabolism; D017474:Receptors, Laminin / Q000378:metabolism; D014407:Tumor Cells, Cultured / Q000276:immunology / Q000378:metabolism / Q000473:pathology
D015703:Antigens, CD; D011508:Chondroitin Sulfate Proteoglycans; D005353:Fibronectins; D039482:Integrin alpha5; D039503:Integrin alpha6; D039121:Integrin alpha6beta1; D019012:Integrin beta1; D016023:Integrins; D007797:Laminin; D017469:Receptors, Fibronectin; D017474:Receptors, Laminin