Identification and Regulation of NRNP1, a Novel Nutritionally Regulated Gene Involved in Cell Death

Abstract

Obesity and Type II diabetes are co‐morbidities that are increasing at an alarming rate in the United States. A thorough understanding of the genes expressed in white adipose tissue (WAT) and the role of these genes in energy metabolism has high relevance to development of new approaches to treat diseases of dysregulated adipose tissue function. Here, we report a novel adipocyte‐enriched gene NRNP1 (Nutritionally Regulated Nuclear Protein 1) which we discovered via in silico data‐mining of whole transcriptome profiling studies of in vitro adipogenic conversion of murine 3T3‐L1 preadipocytes to adipocytes. Ectopic expression studies of NRNP1‐eGFP fusion protein in COS7 cells revealed strong localization of NRNP1 to the cell nucleus, as well as punctate cytoplasmic localization. Western blot analysis of cell lysates from 293T cells transfected with Flag‐tagged NRNP1 indicated a mass of ~22 kDa. Interestingly, such studies revealed that ectopic expression of NRNP1 in 293T cells resulted in cell death with an ~80% reduction in cell number at 24 hrs post‐transfection. The underlying mechanism for this was investigated utilizing western blot studies for apoptotic marker proteins and with DNA fragmentation analysis. In adipogenesis NRNP1 is under strong developmental control with NRNP1 transcript induced > 500‐fold during conversion of 3T3‐L1 preadipocytes to adipocytes. A similar high degree of differentiation‐dependent induction of NRNP1 transcript was observed in an in vitro model of brown adipogenesis and in adipogenesis of primary murine preadipocytes. Strong nutritional regulation of NRNP1 was noted in vivo as NRNP1 transcript was significantly increased in subcutaneous WAT (12‐fold) and in brown adipose tissue (BAT) (3‐fold) of mice that were fasted and then refed vs. levels in fasting mice. The observation of a 12‐fold increase in NRNP1 transcript level in fatty liver of ob/ob mice vs. C57BL/6J mice suggests increased NRNP1 levels may be linked to dysregulated lipid metabolism. Assessment of a broad panel of mouse tissues by qPCR indicated selective enrichment of NRNP1 in WAT depots and BAT. Together, these data support a role for NRNP1 in normal and abnormal lipid metabolism and indicate that mis‐expression of NRNP1 in non‐adipose cells can promote cell death.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.