RNA binding proteins PCBP1 and PCBP2 regulate pancreatic β cell translation.

OBJECTIVES: Tight control of β cell mRNA translation plays a central role in regulating glucose homoeostasis and β cell health. RNA binding proteins (RBPs) impact translational dynamics and function in networks to achieve their regulatory outcomes, yet an understanding of the RBPs and nature of their interplay in directing β cell translation remain limited. We recently established that the RBP PCBP2 is a key post-transcriptional regulator of β cell function. Here, we investigate the relationship of PCBP2 and its sister-isoform PCBP1 in shaping β cell homeostasis and translation. METHODS: Mice with β cell-specific deletion of Pcbp1 and combined Pcbp1/2 were generated to examine the influence of these factors on blood glucose and β cell homeostasis. Gene expression was interrogated with single-cell RNA sequencing, qRT-PCR, and western blot. RNA-protein interactions were measured using RNA immunoprecipitation. Gene depletion studies were performed using CRISPR-Cas9 or shRNAs. Puromycin labeling was used to monitor global translation. RESULTS: Pcbp1 deletion preserved glucose homeostasis whereas Pcbp co-deletion resulted in severe diabetes due to compromised β cell viability. Single-cell RNA sequencing of Pcbp co-deficient β cells revealed downregulation of a network of core translation initiation factors and ribosomal mRNAs. Motif enrichment analysis, mRNA-protein interaction, and mRNA stability studies identified that the PCBPs co-impact these mRNAs in part through binding and stabilization. Accordingly, protein translational monitoring demonstrated a requirement for the PCBPs in sustaining global mRNA translation in β cells. CONCLUSIONS: Our findings demonstrate a requirement for the PCBPs in sustaining the global rates of mRNA translation critical for β cell control of glucose homeostasis.