Drosophila canopy b is a cochaperone of glycoprotein 93

Crystal Morales; Zihai Li

doi:10.1074/jbc.M116.755538

Drosophila canopy b is a cochaperone of glycoprotein 93

Crystal Morales^‡,^§ and
Zihai Li^‡¹

From the ^‡Department of Microbiology and Immunology, Medical University of South Carolina, Charleston, South Carolina 29425 and
the ^§Department of Immunology, University of Connecticut Health Center, Farmington, Connecticut 06030

↵1 To whom correspondence should be addressed. E-mail: zihai{at}musc.edu.

Edited by Luke O'Neill

Abstract

Drosophila gp93 was identified as the ortholog of the mammalian endoplasmic reticulum-resident chaperone gp96. gp93 was found capable of rescuing gp96 client proteins, such as Toll-like receptors (TLRs) and integrins, in a gp96-deficient murine cell line. Mammalian gp96 was further found to require the cochaperone canopy 3 (CNPY3) for proper folding and expression of TLRs, but not integrins. In Drosophila, two possible CNPY family members have been identified but have not yet been characterized. Therefore, we sought to determine the role of Drosophila CNPYa and CNPYb in gp93 biology. Because of higher similarities between CNPY3 and CNPYb, we postulated that CNPYb would be a TLR-specific cochaperone of gp93. Indeed, CNPYb addition in gp93-expressing cells improved TLR expression. CNPYb and gp93 were further found to physically interact. Mutational analysis of cysteine residues in CNPYb identified differential dependence of these cysteines in chaperone function. Our study is the first to characterize Drosophila CNPY molecules. We further uncover more gp93 biology by identifying CNPYb as a cochaperone. A better understanding of this simpler Drosophila system will enable application to the mammalian system, such as has been done with Escherichia coli, yeast, and mammalian HSP90.

Footnotes

This work was supported by National Institutes of Health Grant R01AI070603. The authors declare that they have no conflicts of interest with the contents of this article. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.
This article contains supplemental Fig. S1.