TY - JOUR
T1 - A prominent role of PDIA6 in processing of misfolded proinsulin
AU - Gorasia, Dhana G
AU - Dudek, Nadine L
AU - Safavi-Hemami, Helena
AU - Perez, Rochelle Ayala
AU - Schittenhelm, Ralf B
AU - Saunders, Philippa M
AU - Wee, Sheena
AU - Mangum, Jon E
AU - Hubbard, Michael J
AU - Purcell, Anthony W
PY - 2016
Y1 - 2016
N2 - Despite its critical role in maintaining glucose homeostasis, surprisingly little is known about proinsulin folding in the endoplasmic reticulum. In this study we aimed to understand the chaperones involved in the maturation and degradation of proinsulin. We generated pancreatic beta cell lines expressing FLAG-tagged proinsulin. Several chaperones (including BiP, PDIA6, calnexin, calreticulin, GRP170, Erdj3 and ribophorin II) co-immunoprecipitated with proinsulin suggesting a role for these proteins in folding. To investigate the chaperones responsible for targeting misfolded proinsulin for degradation, we also created a beta cell line expressing FLAG-tagged proinsulin carrying the Akita mutation (Cys96Tyr). All chaperones found to be associated with wild type proinsulin also co-immunoprecipitated with Akita proinsulin. However, one additional protein, namely P58(IPK), specifically precipitated with Akita proinsulin and approximately ten fold more PDIA6, but not other PDI family members, was bound to Akita proinsulin. The latter suggests that PDIA6 may act as a key reductase and target misfolded proinsulin to the ER-degradation pathway. The preferential association of PDIA6 to Akita proinsulin was also confirmed in another beta cell line (βTC-6). Furthermore, for the first time, a physiologically relevant substrate for PDIA6 has been evidenced. Thus, this study has identified several chaperones/foldases that associated with wild type proinsulin and has also provided a comprehensive interactome for Akita misfolded proinsulin.
AB - Despite its critical role in maintaining glucose homeostasis, surprisingly little is known about proinsulin folding in the endoplasmic reticulum. In this study we aimed to understand the chaperones involved in the maturation and degradation of proinsulin. We generated pancreatic beta cell lines expressing FLAG-tagged proinsulin. Several chaperones (including BiP, PDIA6, calnexin, calreticulin, GRP170, Erdj3 and ribophorin II) co-immunoprecipitated with proinsulin suggesting a role for these proteins in folding. To investigate the chaperones responsible for targeting misfolded proinsulin for degradation, we also created a beta cell line expressing FLAG-tagged proinsulin carrying the Akita mutation (Cys96Tyr). All chaperones found to be associated with wild type proinsulin also co-immunoprecipitated with Akita proinsulin. However, one additional protein, namely P58(IPK), specifically precipitated with Akita proinsulin and approximately ten fold more PDIA6, but not other PDI family members, was bound to Akita proinsulin. The latter suggests that PDIA6 may act as a key reductase and target misfolded proinsulin to the ER-degradation pathway. The preferential association of PDIA6 to Akita proinsulin was also confirmed in another beta cell line (βTC-6). Furthermore, for the first time, a physiologically relevant substrate for PDIA6 has been evidenced. Thus, this study has identified several chaperones/foldases that associated with wild type proinsulin and has also provided a comprehensive interactome for Akita misfolded proinsulin.
KW - Animals
KW - Cell Line
KW - Mice
KW - Mutagenesis, Site-Directed
KW - Proinsulin/chemistry
KW - Protein Disulfide-Isomerases/chemistry
KW - Protein Folding
U2 - 10.1016/j.bbapap.2016.03.002
DO - 10.1016/j.bbapap.2016.03.002
M3 - Journal article
C2 - 26947243
VL - 1864
SP - 715
EP - 723
JO - Biochimica et Biophysica Acta - Reviews on Cancer
JF - Biochimica et Biophysica Acta - Reviews on Cancer
SN - 0304-419X
IS - 6
ER -