The ATPase activity of Asna1/TRC40 is required for pancreatic progenitor cell survival

Abstract

Asna1, also known as TRC40, is implicated in delivery of tail anchored (TA) proteins into the ER, in vesicle-mediated transport, and in chaperoning unfolded proteins during oxidative stress/ATP depletion. We recently showed that Asna1 inactivation in β-cells resulted in impaired retrograde transport, ER stress and diabetes in mice. Here we show that Asna1 inactivation in pancreatic progenitor cells leads to redistribution of the Golgi TA SNAREs Syntaxin-5 and Syntaxin-6, Golgi fragmentation, and accumulation of cytosolic p62+ puncta. Asna1−/− multipotent progenitor cells (MPCs) selectively activate integrated stress response signalling and undergo apoptosis, thereby disrupting endocrine and acinar cell differentiation, resulting in pancreatic agenesis. Rescue experiments implicate the Asna1 ATPase activity and CXXC di-cysteine motif in ensuring Golgi integrity, Syntaxin-5 localization and MPC survival. Ex vivo inhibition of retrograde transport reproduces the perturbed Golgi morphology and Syntaxin-5 and Syntaxin-6 expression, whereas modulation of p53 activity using PFT-α and Nutlin-3, prevents or reproduces apoptosis in Asna1 deficient and wildtype MPCs, respectively. These findings support a role for the Asna1 ATPase activity in ensuring survival of pancreatic MPCs, possibly by counteracting p53 mediated apoptosis.