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

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.

Insights into the Pathophysiology of Infertility in Females with Classical Galactosaemia

“…Kim et al, has confirmed the pivotal role of PTEN–PI3K signalling in the activation of primordial follicles [60]. We propose that dysregulation of the PTEN–PI3K signalling pathway in galactosaemia patients was identified in our studies and in the Gal deficient mouse model may be implicated in the primordial follicular dysgenesis observed in galactosaemia (Figure 1b) [17,18].…”

“…The up-regulation of PTEN was also demonstrated in the human GC study of Coss et al (2014), as described earlier [17]. Salubrinal, a chemical compound that alleviates ER stress when administered to mutant mouse fibroblast cell lines normalised the down regulated PI3/Akt signalling pathway and the premature loss of primordial follicles seen in young mutant mice [18].…”

“…The key enzymes involved are shaded. ( b ) Illustration of the steps in oogenesis and folliculogenesis over the prenatal to menopause time period that may be influenced by GALT deficiency [16,17,18,19,20] with the proposed site of the PI3K/AKT regulation as cited by Sanchez and Smitz [20]. The abbreviations used are listed in the abbreviations list.…”

“…In the GALT deficient mouse model that demonstrated a subfertility phenotype in adult females, Balakrishnan et al identified that GALT is a positive regulator of the PI3K/Akt signalling pathway [18]. The protein expression of BiP and PTEN (negative regulator) of the PI3K/Akt signalling pathway was higher in GALT deficiency.…”

Optimized platelet rich plasma releasate (O-rPRP) repairs galactosemia-induced ovarian follicular loss in rats by activating mTOR signaling and inhibiting apoptosis

“…Previously, FSH treatment was found to activate the mTOR pathway and inhibit autophagy, but this effect was abolished in the presence of an AKT phosphorylation inhibitor [ 54 ]. In a previous report, there was an association between aberrant mTOR/Akt signaling and galactosemia [ 55 ]. According to the results reported here, we suggest that galactose stress induced miR-223, which targeted β1 integrin expression and resulted in impairing AKT phosphorylation and the downstream mTOR pathway.…”