ASNA-1 Activity Modulates Sensitivity to Cisplatin

Abstract

Cancer can be cured by platinum-based chemotherapy, but resistance is a major cause of treatment failure. Here we present the nematode Caenorhabditis elegans as a model to study interactions between the platinum drug cisplatin and signaling pathways in vivo. Null mutation in a single gene, asna-1, makes worms hypersensitive to cisplatin. The metalloregulated ATPase ASNA-1 promotes insulin secretion and membrane insertion of tail-anchored proteins. Using structural data from ASNA-1 homologues, we identify specific ASNA-1 mutants that are sensitive to cisplatin while still able to promote insulin signaling. Mutational analysis reveals that hypersensitivity of ASNA-1 mutants to cisplatin remains in absence of CEP-1/p53 or apoptosis. Human ASNA1 can substitute for the worm gene, indicating a conserved function. Cisplatin sensitivity is not affected by decreased insulin signaling in wild-type nematodes or restored insulin signaling in asna-1 mutants. These findings provide a functional insight into ASNA-1, demonstrate that C. elegans can be used to characterize cisplatin resistance mechanisms, and suggest that rationally designed drugs against ASNA-1 can sensitize cancer cells to cisplatin.

The Protein Targeting Factor Get3 Functions as ATP-Independent Chaperone under Oxidative Stress Conditions

“…These results explain previous findings that the cellular abundance of Get3 (~17,300 molecules) is up to 10 times higher than that of other members of the GET pathway, such as Get1 (~2,250 molecules), and matches well with the abundance of other molecular chaperones, including Hsp104 (~32,800 molecules) (Ghaemmaghami et al, 2003). Our finding that Get3 appears to serve a dual purpose in vivo is also in excellent agreement with previous studies conducted in Caenorhabditis elegans , which revealed that deletion of the Get3 homologue TRC40 (ASNA1) causes two distinct phenotypes, a severe growth defect and increased sensitivity to cisplatin (Hemmingsson et al, 2010), an anti-cancer drug known to cause oxidative stress. Intriguingly, while both phenotypes were rescued by expression of wild-type TRC40, a TRC40-variant lacking the conserved, redox-sensitive cysteines rescued the growth defect but not the cisplatin-sensitivity (Hemmingsson et al, 2010).…”

“…Our finding that Get3 appears to serve a dual purpose in vivo is also in excellent agreement with previous studies conducted in Caenorhabditis elegans , which revealed that deletion of the Get3 homologue TRC40 (ASNA1) causes two distinct phenotypes, a severe growth defect and increased sensitivity to cisplatin (Hemmingsson et al, 2010), an anti-cancer drug known to cause oxidative stress. Intriguingly, while both phenotypes were rescued by expression of wild-type TRC40, a TRC40-variant lacking the conserved, redox-sensitive cysteines rescued the growth defect but not the cisplatin-sensitivity (Hemmingsson et al, 2010). These results indicate that TRC40 works as a dual-function protein also in higher eukaryotes.…”

Protein Quality Control under Oxidative Stress Conditions

“…However, only wild-type TRC40 was able to complement for the observed cisplatin sensitivity. These results strongly suggest that Get3’s redox-regulated chaperone functions plays a crucial role in oxidative stress protection in higher eukaryotes as well (119). These are exciting findings but many questions remain open: How does Get3 recognize its client proteins?…”

“…These findings are consistent with previous reports about a potential dual function in the Get3 homologue TRC40 in Caenorhabditis elegans . Deletion of TRC40 was found to cause severe growth deficits and increased sensitivity towards cisplatin (119), an anticancer drug thought to cause oxidative stress in vivo (120). Importantly, complementation studies using either wild-type TRC40 or a mutant variant lacking two of the four cysteines revealed that both proteins rescued the growth defect of a TRC40 deletion strain.…”

Asna1/TRC40 Controls β-Cell Function and Endoplasmic Reticulum Homeostasis by Ensuring Retrograde Transport

“…Recently, Get3/Asna1 was also shown to function, under oxidative stress conditions, as a molecular chaperone that binds unfolded proteins to prevent their irreversible aggregation (18). In Caenorhabditis elegans, Asna1 function is required for larval growth and resistance to cisplatin, an oxidative stress-inducing anticancer drug (19,20).…”