Reversal of aberrant PI3K/Akt signaling by Salubrinal in a GalT-deficient mouse model

Highlights

• Heightened ER stress is seen in galactosemic patients and mouse model of the disease.

• Reduced PI3K/Akt signaling occurs in GALT-ve human and GalT-ve mouse cells.

• ER stress reducer Salubrinal normalizes PI3K/Akt signaling in GalT-ve mouse tissues.

• Salubrinal delays premature follicular and Purkinje cell loss in GalT-ve mice.

Abstract

Classic Galactosemia is an autosomal recessive disorder caused by deleterious mutations in the GALT gene, which encodes galactose-1 phosphate uridylyltransferase enzyme (GALT: EC 2.7.7.12). Recent studies of primary skin fibroblasts isolated from the GalT-deficient mice demonstrated a slower growth rate, a higher level of endoplasmic reticulum (ER) stress, and down-regulation of the Phosphoinositide 3 kinase/Protein kinase B (PI3K/Akt) signaling pathway. In this study, we compared the expression levels of the PI3K/Akt signaling pathway in normal and GalT-deficient mouse tissues. In mutant mouse ovaries, phospho-Akt [pAkt (Ser473)] and pGsk3β were reduced by 62.5% and 93.5%, respectively (p < 0.05 versus normal controls). In mutant cerebella, pAkt (Ser473) and pGsk3β were reduced by 62%, 50%, respectively (p < 0.05). To assess the role of ER stress in the down-regulation of PI3K/Akt signaling, we examined if administration of Salubrinal, a chemical compound that alleviates ER stress, to GalT-deficient fibroblasts and animals could normalize the pathway. Our results demonstrated that Salubrinal effectively reversed the down-regulated PI3K/Akt signaling pathway in the mutant cells and animals to levels close to those of their normal counterparts. Moreover, we revealed that Salubrinal can significantly slow down the loss of Purkinje cells in the cerebella, as well as the premature loss of primordial ovarian follicles in young mutant mice. These results open the door for a new therapeutic approach for the patients with Classic Galactosemia.