The CACNA1F Gene Encodes an L-Type Calcium Channel with Unique Biophysical Properties and Tissue Distribution

Glutamate release from rod photoreceptors is dependent on a sustained calcium influx through L-type calcium channels. Missense mutations in the CACNA1F gene in patients with incomplete X-linked congenital stationary night blindness implicate the Ca v 1.4 calcium channel subtype. Here, we describe the functional and pharmacological properties of transiently expressed human Ca v 1.4 calcium channels. Ca v 1.4 is shown to encode a dihydropyridine-sensitive calcium channel with unusually slow inactivation kinetics that are not affected by either calcium ions or by coexpression of ancillary calcium channel β subunits. Additionally, the channel supports a large window current and activates near -40 mV in 2 mM external calcium, making Ca v 1.4 ideally suited for tonic calcium influx at typical photoreceptor resting potentials. Introduction of base pair changes associated with four incomplete X-linked congenital night blindness mutations showed that only the G369D alteration affected channel activation properties. Immunohistochemical analyses show that, in contrast with previous reports, Ca v 1.4 is widely distributed outside the retina, including in the immune system, thus suggesting a broader role in human physiology.