Effect of tunicamycin on sialomucin and natural killer susceptibility of rat mammary tumor ascites cells.
The MAT-B1 and MAT-C1 ascites sublines of the 13762 rat mammary adenocarcinoma contain a dominant cell surface "complex" consisting of two glycoproteins: ascites sialoglycoprotein (ASGP)-1, a Mr 600,000-700,000 peanut agglutinin-binding sialomucin, and ASGP-2, a Mr 120,000 concancavalin A-binding glycoprotein (Sherblom et al., J. Biol. Chem., 255: 783-790, 1980; Sherblom and Carraway, J. Biol. Chem., 255: 12051-12059, 1980). Although both cell lines are resistant to lysis by natural killer cells, treatments which result in loss of cell surface ASGP-1 render the cells susceptible to natural killer cell lysis (Sherblom and Moody, Cancer Res., 46:4543-4546, 1986). Treatment of the ascites cells with 5 micrograms/ml tunicamycin for 24 h effectively inhibits glycosylation of ASGP-2 without affecting cell viability or total protein synthesis. Under these conditions, expression of ASGP-1 is depressed by at least 50% in both cell lines, as monitored by [3H]glucosamine incorporation and by binding of peanut agglutinin to intact cells. The size distribution of O-linked oligosaccharides in ASGP-1 from tunicamycin-treated versus control MAT-B1 cells is indistinguishable, as determined by Bio-Gel P-4 chromatography following alkaline-borohydride treatment. Complex isolated from either treated or control cells bands at the same density in a CsCl gradient containing Triton X-100 and contains a diffuse band corresponding to ASGP-2 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Tunicamycin-treated cells, consistent with the reduced expression of ASGP-1, are significantly more susceptible to natural killer cell-mediated lysis, when compared to untreated controls. The results suggest that N-linked glycosylation is a prerequisite for sialomucin synthesis and/or complex formation.
Bharathan
S
S
Department of Biochemistry, University of Maine, Orono 04469.
Moriarty
J
J
Moody
C E
CE
Sherblom
A P
AP
D000230:Adenocarcinoma / Q000276:immunology / Q000503:physiopathology*; D000818:Animals; D003602:Cytotoxicity, Immunologic; D005260:Female; D005944:Glucosamine / Q000378:metabolism; D007694:Killer Cells, Natural / Q000276:immunology*; D037102:Lectins; D007930:Leucine / Q000378:metabolism; D008325:Mammary Neoplasms, Experimental / Q000276:immunology / Q000503:physiopathology*; D008562:Membrane Glycoproteins / Q000302:isolation & purification / Q000378:metabolism; D008970:Molecular Weight; D055264:Mucin-4; D009363:Neoplasm Proteins / Q000378:metabolism*; D051381:Rats; D011916:Rats, Inbred F344; D012795:Sialoglycoproteins / Q000302:isolation & purification / Q000378:metabolism*; D014407:Tumor Cells, Cultured / Q000276:immunology / Q000502:physiology; D014415:Tunicamycin / Q000494:pharmacology*
D037102:Lectins; D008562:Membrane Glycoproteins; D055264:Mucin-4; D009363:Neoplasm Proteins; D012795:Sialoglycoproteins; D014415:Tunicamycin; D007930:Leucine; D005944:Glucosamine