TRPM6 and renal tubular acidosis: Na-K-ATPase, sodium-potassium pump; RTA, renal tubular acidosis; mTOR, mechanistic (or mammalian) target of rapamycin; HDACi, histone deacetylase inhibitor; PD-1, programmed death-1; EGFR-1, epidermal growth factor receptor-1; TRPM6/7, transient receptor potential cation channel subfamily M member 6/7