TRPM5 and posterior cortical atrophy: For instance, TRPV5 and TRPV6 display the largest PCa/PNa (>100), while TRPM4 and TRPM5 are virtually impermeable to Ca2+ (PCa/PNa < 0.01), although they are gated by an increase in [Ca2+]i (Gees et al., 2010).