Mouse myeloma mutants blocked in the assembly, glycosylation and secretion of immunoglobulin

Abstract

Two stable mutant cell lines derived from the MPC-11 mouse myeloma synthesize immunoglobulin with abnormal heavy chains and normal light chains. The mutant heavy chains have molecular weights of 38,000 to 42,000 (M3.11) and 50,000 (ICR 11.19) as compared to 55,000 of the wild type. The mutants demonstrate a variety of blocks in the assembly, glycosylation and secretion of immunoglobulin. (1) The wild type assembles and secretes 90% of its immunoglobulin primarily as H 2 L 2 while M3.11 is partially blocked in the assembly of H 2 L 2 , and secretes approximately one half of its immunoglobulin as HL. ICR 11.19, with a more complete block in interchain disulfide bond formation, assembles less than 10% of its immunoglobulin into H 2 L 2 , has a block in secretion and degrades most of its immunoglobulin. (2) M3.11 uses only one of the two wild type pathways of assembly. Reduction of isolated H 2 L 2 with 2-mercapthoethanol suggests an altered stability of the inter-H chain disulfide bonds in M3.11 as compared to the wild type immunoglobulin. (3) While the parent glycosylates all of its heavy chains, M3.11 does not attach any carbohydrate to 30 to 50% of its heavy chains. These non-glycosylated heavy chains are, nonetheless, assembled and secreted with similar kinetics to the glycosylated heavy chain.