title: Interallelic complementation of beta-subunit defects in fibroblasts of patients with propionyl-CoA carboxylase deficiency microinjected with mutant cDNA constructs.
abstract: Propionic acidemia results from deficiency of propionyl-CoA carboxylase (PCC) activity. PCC is a biotin-dependent, mitochondrial enzyme composed of alpha- and beta-subunits (structure, alpha 4 beta 4), with the alpha-subunit containing the biotin ligand. About two-thirds of fibroblast lines from patients with mutations in the PCCB (beta-subunit) gene show interallelic complementation in cell fusion experiments (the pccB and pccC subgroups of the pccBC major group defining beta-subunit mutations, where pccB x pccC fusions show complementation). We previously identified the mutations in several pccB or pccC cell lines and suggested that point mutations or small, in-frame insertions or deletions were likely responsible for the complementation obtained between beta-subunit defects. To test this hypothesis, we have introduced five different mutations (three pccB and two pccC) that fit these criteria into a PCC beta-subunit cDNA plasmid expressed from a cytomegalovirus promoter. The cDNA plasmids were microinjected into mutant fibroblasts and the cells were assayed by radioautographic detection of 14C-propionate incorporation into cellular macromolecules. Four different mutations (Pro228Leu or dupKICK140 from pccB or delta IIe408 or Arg410Trp from pccC) complemented cells from complementation subgroups in a pattern congruent with the results obtained in cell fusion experiments. The fifth mutation, Arg536Asn, which was found both in a complementing pccB and a non-complementing pccBC cell line, failed to complement any of the mutant cell lines.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: McGill University-Montreal Children's Hospital Research Institute, Quebec, Canada.
authors.forename: M
authors.initials: M
authors.lastname: Loyer
authors.forename: D
authors.initials: D
authors.lastname: Leclerc
authors.forename: R A
authors.initials: RA
authors.lastname: Gravel
mesh_terms: D000592:Amino Acid Metabolism, Inborn Errors / Q000097:blood / Q000201:enzymology / Q000235:genetics*; D002262:Carboxy-Lyases / Q000172:deficiency / Q000235:genetics* / Q000378:metabolism; D002460:Cell Line; D018076:DNA, Complementary; D005347:Fibroblasts / Q000166:cytology; D005816:Genetic Complementation Test; D006801:Humans; D043586:Methylmalonyl-CoA Decarboxylase; D008845:Microinjections; D009154:Mutation; D010957:Plasmids; D011422:Propionates / Q000097:blood*
chemical_list: D018076:DNA, Complementary; D011422:Propionates; D002262:Carboxy-Lyases; D043586:Methylmalonyl-CoA Decarboxylase; C029658:propionic acid