Retention of transformant specific type III collagen in dibutyryl cAMP treated Kirsten sarcoma virus transformed BALB 3T3 cells and in a flat revertant

Abstract

AbstractWe previously reported that Kirsten sarcoma virus transformed BALB 3T3 (Ki‐3T3) cell cultures contained mainly type I collagen and about 30% of another type designated by us as Y and which appears to be type III collagen, [α1 (III)]3. Clones of BALB 3T3 which exhibited contact‐inhibition were found to contain mainly type I collagen [α1(I)]2α2, and about 25% of another type (X) which was composed of three α1 chains differing from those of type III (Hata, R. and B. Peterkofsky, 1977 Proc. Nat. Acad. Sci. (U.S.A.), 74: 2933—2937). Since dibutyryl 3′:5′ cyclic adenosine monophosphate (dbcAMP) increases collagen synthesis and alters other transformation specific properties of Ki‐3T3 cells, we determined whether treatment of Ki‐3T3 cells with this compound restored the normal collagen phenotype. We also analyzed the collagen of a revertant of Ki‐3T3 which exhibits properties similar to those of the dbcAMP treated transformant. Procollagen labeled with radioactive proline was isolated from the medium or cells of cultures and was converted to collagen with pepsin; the collagen was analyzed by carboxymethyl cellulose (CMC) chromatography or gel electrophoresis under denaturing conditions. Ki‐3T3 cells treated with 0.5 mM dbcAMP continued to accumulate type III collagen but there was an increase in the number of α1 chains eluting from CMC columns in the same position as α1 (I) suggesting increased accumulation of type X collagen. Although the revertant was similar to dbcAMP treated cells in that it exhibited a flattened morphology and a high relative rate of collagen synthesis, the collagen profile was similar to that of the transformant, consisting mainly of types I and III. These results indicate that accumulation of type III collagen is unaffected by dbcAMP but suggest that cAMP may be involved in the regulation of type X collagen. The failure of dbcAMP or reversion to affect the occurrence of type III collagen supports the mechanism of cell selection as a means of explaining the specific occurrence of type III collagen in sarcoma virus transformed 3T3 cells.