tailieunhanh - Báo cáo khoa học: The heat shock protein 70 molecular chaperone network in the pancreatic endoplasmic reticulum ) a quantitative approach

Traditionally, the canine pancreatic endoplasmic reticulum (ER) has been the workhorse for cell-free studies on protein transport into the mamma-lian ER. These studies have revealed multiple roles for the major ER-lumi-nal heat shock protein (Hsp) 70, IgG heavy chain-binding protein (BiP), at least one of which also involves the second ER-luminal Hsp70, glucose-reg-ulated protein (Grp) 170. | ỊFEBS Journal The heat shock protein 70 molecular chaperone network in the pancreatic endoplasmic reticulum - a quantitative approach Andreas Weitzmann Christiane Baldes Johanna Dudek and Richard Zimmermann Medizinische Biochemie und Molekularbiologie Universitat des Saarlandes Homburg Germany Keywords BiP endoplasmic reticulum J-domains nucleotide exchange factors molecular chaperones Correspondence R. Zimmermann Medizinische Biochemie und Molekularbiologie Universitat des Saarlandes D-66421 Homburg Germany Fax 49 6841 1626288 Tel 49 6841 1626510 E-mail bcrzim@ Received 15 June 2007 revised 9 August 2007 accepted 10 August 2007 doi Traditionally the canine pancreatic endoplasmic reticulum ER has been the workhorse for cell-free studies on protein transport into the mammalian ER. These studies have revealed multiple roles for the major ER-lumi-nal heat shock protein Hsp 70 IgG heavy chain-binding protein BiP at least one of which also involves the second ER-luminal Hsp70 glucose-regulated protein Grp 170. In addition at least one of these BiP activities depends on Hsp40. Up to now five Hsp40s and two nucleotide exchange factors Sill and Grp170 have been identified in the ER of different mammalian cell types. Here we quantified the various proteins of this chaperone network in canine pancreatic rough microsomes. We also characterized the various purified proteins with respect to their affinities for BiP and their effect on the ATPase activity of BiP. The results identify Grp170 as the major nucleotide exchange factor for BiP and the resident ER-membrane proteins ER-resident J-domain protein 1 plus ER-resident J-domain protein 2 Sec63 as prime candidates for cochaperones of BiP in protein transport in the pancreatic ER. Thus these data represent a comprehensive analysis of the BiP chaperone network that was recently linked to two human inherited diseases polycystic liver disease and Marinesco-Sjogren syndrome. The initial step .