TRPV4 and posterior cortical atrophy: Biophysically, TRPV4 is characterized as a non-selective cation channel with a moderately high Ca2+ permeability ratio of PCa/PNa = 6-10 (16–18) with two aspartate residues (Asp672 and Asp682) dictating the Ca2+ selectivity of the TRPV4 pore (16).