BioChem - DOS

Proinsulin folding and trafficking defects trigger a common pathological disturbance of endoplasmic reticulum homeostasis

Protein science : a publication of the Protein Society

Arunagiri, Anoop; Alam, Maroof; Haataja, Leena; Draz, Hassan; Alasad, Bashiyer; Samy, Praveen; Sadique, Nadeed; Tong, Yue; Cai, Ying; Shakeri, Hadis; Fantuzzi, Federica; Ibrahim, Hazem; Jang, Insook; Sidarala, Vaibhav; Soleimanpour, Scott A.; Satin, Leslie S.; Otonkoski, Timo; Cnop, Miriam; Itkin‐ Ansari, Pamela; Kaufman, Randal J.; Liu, Ming; Arvan, Peter

<P><B>Abstract</B><P>Primary defects in folding of mutant proinsulin can cause dominant&#x2010;negative proinsulin accumulation in the endoplasmic reticulum (ER), impaired anterograde proinsulin trafficking, perturbed ER homeostasis, diminished insulin production, and &beta;&#x2010;cell dysfunction. Conversely, if primary impairment of ER&#x2010;to&#x2010;Golgi trafficking (which also perturbs ER homeostasis) drives misfolding of nonmutant proinsulin-this might suggest bi&#x2010;directional entry into a common pathological phenotype (proinsulin misfolding, perturbed ER homeostasis, and deficient ER export of proinsulin) that can culminate in diminished insulin storage and diabetes. Here, we've challenged &beta;&#x2010;cells with conditions that impair ER&#x2010;to&#x2010;Golgi trafficking, and devised an accurate means to assess the relative abundance of distinct folded/misfolded forms of proinsulin using a novel nonreducing SDS&#x2010;PAGE/immunoblotting protocol. We confirm abundant proinsulin misfolding upon introduction of a diabetogenic <I>INS</I> mutation, or in the islets of <I>db/db</I> mice. Whereas blockade of proinsulin trafficking in Golgi/post&#x2010;Golgi compartments results in intracellular accumulation of properly&#x2010;folded proinsulin (bearing native disulfide bonds), impairment of ER&#x2010;to&#x2010;Golgi trafficking (regardless whether such impairment is achieved by genetic or pharmacologic means) results in decreased native proinsulin with more misfolded proinsulin. Remarkably, reversible ER&#x2010;to&#x2010;Golgi transport defects (such as treatment with brefeldin A or cellular energy depletion) upon reversal quickly restore the ER folding environment, resulting in the disappearance of pre&#x2010;existing misfolded proinsulin while preserving proinsulin bearing native disulfide bonds. Thus, proper homeostatic balance of ER&#x2010;to&#x2010;Golgi trafficking is linked to a more favorable proinsulin folding (as well as trafficking) outcome.</P></P>

2024

Wiley (John WileySons)

0961-8368

1469-896x

33

4

pp.e4949

10.1002/pro.4949

http://click.ndsl.kr/servlet/OpenAPIDetailView?keyValue=05787966&target=NART&cn=NART129539438