We examined the role of the cysteine string protein (Csp) in cystic fibrosis transmembrane
conductance regulator (CFTR) biogenesis in relation to another J-domain protein, Hdj-2, a
recognized CFTR cochaperone. Increased expression of Csp produced a dose-dependent
reduction in mature (band C) CFTR and an increase in immature (band B) CFTR.
Exogenous expression of Hdj-2 also increased CFTR band B, but unlike Csp, Hdj-2
increased band C as well. The Csp-induced block of CFTR maturation required Hsp70 …