cX	concentration of ion species X
pHi	refers to the internal pH, either the luminal/intra-lysosomal pH in SSME recordings, or the cytosolic pH in APC
pHo	refers to the external pH: in SSME recordings the cytosolic pH; in APC recordings the luminal/intra-lysosomal pH
I	current, in SSME referring to the peak current, in patch-clamp to the steady-state current; depends on the ion species and the driving forces (ion gradients and voltage)
Imax	maximum current, usually obtained from EC50 or IC50 fits
Imin	minimum current, usually obtained from EC50 or IC50 fits
pKa	pK value for downregulation of TMEM175 in acidic environments, obtained from a pH dependent fit of the recorded peak currents, using equations that consider either a single (I = Imax/(1 + 10pKa−pH)) or two (I = Imax1/(1 + 10pKa1-pH) + Imax2/(1 + 10pKa2−pH)) pK values
pKb	pK value for downregulation of TMEM175 in alkaline environments, obtained from a pH dependent fit of the recorded peak currents, using I = Imax/(1 + 10pH-pKb)
EC50	empirical half saturation constant for a dose response curve of an enhancer/activator, obtained from the fit using the equation I = Imax − (Imax − Imin)/(1 + (c/EC50)n)
IC50	same as EC50, used for dose response curves of inhibitors
n	Hill coefficient, used in EC50 and IC50 fits
PX	Permeability for ion species X