Novel anti-aging gene NM_026333 contributes to proton-induced aging via NCX1-pathway.

Diet-induced metabolic acidosis is associated with the impairment of bone metabolism and an increased risk of a number of chronic noncommunicable diseases, such as type 2 diabetes mellitus and hypertension. Low serum bicarbonate is associated with high mortality in healthy older individuals. Recently, we demonstrated that both coupling factor 6 (CF6)-overexpressing transgenic (TG) and high salt-fed mice which had sustained intracellular acidosis, due to enhanced proton import through ecto-F1 Fo complex and/or reduced proton export through Na+ -K+ ATPase inhibition, displayed shortened lifespan and early senescence-associated phenotypes such as signs of hair greying and alopecia, weight loss, and/or reduced organ mass. In this study, we searched causative genes of proton-induced aging in CF6-overexpressing TG and high salt-fed mice. We discovered NM_026333 as a novel anti-aging gene which was downregulated in the heart and kidney in both types of mice. NM_026333 protein consists of 269 amino acids with transmembrane region (90-193aa). Induction of NM_026333 or recombinant protein rescued TG cells and CF6-treated human cells from aging hallmarks of impaired autophagy, genomic instability, and epigenetic alteration. NM_026333 protein directly bound plasma membrane Na+ -Ca2+ exchanger 1 (NCX1) to suppress its reverse mode, and cancelled proton-induced epigenetic regression of Atg7 that was caused by H3K4 and H4K20 tri-methylation via suppression of demethylase and H4K5 acetylation via suppression of nuclear HDAC3-HDAC4-emerin system. NM_026333 also attenuated proton-induced impaired formation of autolysosome, an increase in nuclear acetylated LC3 II, and acetylation of Atg7. These effects reappeared by NCX1 inhibitor. Furthermore, NCX1 inhibitor extended lifespan compared with vehicle-treatment in TG mice. This study will shed light on novel aging mechanism and provide implications in a target for anti-aging therapy.