Voltage-sensor protein present on the post-synaptic side of glutamatergic mossy fibers and granule cells in the cerebellum (PubMed:25165868, PubMed:30810529). Despite the presence of a voltage-sensor segment, does not form a functional ion channel and its precise role remains unclear (PubMed:25165868, PubMed:30810529). Undergoes both rapid and slow structural rearrangements in response to changes in voltage (PubMed:30810529). Contains a zinc-binding site that can regulate the slow conformational transition (PubMed:30810529). Homodimer; disulfide-linked. Present in the dendrites and soma of cerebellar granule neurons, but not in their axon. Mainly expressed in the cerebellum (PubMed:25165868). Also expressed in cerebral cortex, skeletal muscle and thyroid, but at much lower levels (PubMed:25165868). The transmembrane segment S4 functions as voltage-sensor and is characterized by a series of positively charged amino acids at every third position (PubMed:30810529). Transplantation of the transmembrane segment S4 into HVCN1, generates a functional voltage-activated proton channel (PubMed:30810529).