In the epididymis and vas deferens, the vacuolar H(+)ATPase (V-ATPase), located in the apical pole of narrow and clear cells, is required to establish an acidic luminal pH. Low pH is important for the maturation of sperm and their storage in a quiescent state. The V-ATPase also participates in the acidification of intracellular organelles. The V-ATPase contains many subunits, and several of these subunits have multiple isoforms. Subunits ATP6VA2 and ATP6V1A were detected in intracellular structures closely associated but not identical to the TGN of principal cells and narrow/clear cells, and subunit ATP6VD1 was strongly expressed in the apical membrane of principal cells in the apparent absence of other V-ATPase subunits. In principal cells, the ATP6VD1 isoform may have a physiological function that is distinct from its role in proton transport via the V-ATPase complex. The agouti-related protein (AgRP) is an orexigenic peptide that plays a significant role in the regulation of energy balance. Using an elaborate in vitro screening approach, we show here that two adjacent enhancers inside the first intron of the neighboring (1.4 kb downstream) ATPase gene (ATP6VD1) modulate the human AgRP promoter with profound spatiotemporal variation despite their diminutive sizes (221 and 231 nt). In transgenic mice, the proximal enhancer displayed specificity for the testis, tail, and ears, and the distal one for the testis, front feet, bone, heart, muscle, brain, spinal cord, and tongue, while dietary fat and overnight fasting had differential effects on enhancer activities. Spatiotemporal expression of the human AgRP gene is influenced by diversified primate-specific intronic sequences in its neighboring ATP6VD1 gene.
ATPase, H+ transporting, lysosomal 38kDa, V0 subunit d1