Proteoglycan characterization in COG7-deficient cells

Abstract

COG is a protein complex (units 1 -8) involved in retrograde transport of the resident Golgi proteins in intra-Golgi retrograde transport. Mutation in cog7 gene leads to congenital disorder of glycosylation (CDG-COG7) which causes severe mental retardation and, in some cases,death. There is significant amount of literature that describes glycosylation disorder in COG7 patients, but there is no data describing PGs from CDG-COG7. Metabollic labelling with WB and MS was performed. COG7 cells secrete high Mw PG with extensive sulfation level. The main modification of the PG in secreted fraction is CS -95% ,and HS comprises of 5 %. Cellular proteolgycans show reduced synthesis of HS 65% compared with healthy 85%. Secreted proteolgycans from COG7 showed reduced PG variation and the presence of serglycin was detected. Intracellular decorin was detected in COG7 cells with possible formation of complexes with collagen type I or type II. Aggrecan PG was detected intracellularly as well as in a secreted form. Distorted recycling mechanism of uptaken proteins was discovered with long delay in release of uptaken protein