Differential Interaction of Coagulation Factor VIII and Factor V with Protein Chaperones Calnexin and Calreticulin

• DOI: 10.1074/jbc.273.14.8537
• Publication Date: 2002-07-26T15:07:12Z
• Authors: Steven W. Pipe; Jill A. Morris; Jay Shah; Randal J. Kaufman
• Keywords: Calnexin; Endoplasmic-reticulum-associated protein degradation; Chaperone (clinical); Lactacystin

Factor VIII (FVIII) and factor V (FV) are homologous coagulation cofactors sharing a similar domain organization (A1-A2-B-A3-C1-C2) both extensively glycosylated within their B-domains. In mammalian cell expression systems, compared with FV, the FVIII primary translation product is inefficiently transported out of endoplasmic reticulum. Here we show that degraded by lactacystin-inhibitable pathway, implicating cytosolic 20 S proteasome machinery. Protein chaperones calnexin (CNX) calreticulin (CRT) preferentially interact glycoproteins containing monoglucosylated <i>N</i>-linked oligosaccharides proposed to traffic proteins through degradative and/or secretory pathways. Utilizing co-immunoprecipitation assays, intracellular was detected in association CNX maximally 30 min 1 h following synthesis, whereas FV could not be CNX. contrast, displayed interaction CRT during transit pathway. B-domain deleted significantly reduced interaction, indicating may represent site. presence inhibitors glucose trimming, interactions CNX, CRT, were secretion FVIII, inhibited. addition, transfection glucosidase I-deficient Chinese hamster ovary line (Lec23) demonstrated degradation inhibited, little effect on FV. These results support binding, mediated at least part required for efficient secretion. does require The suggest unique requirement carbohydrate processing molecular chaperone limit productive FVIII.