voltage-dependent Ca+2 channel alpha-1H (T-type, Cav3.2, low-voltage-activated Ca+2 channel alpha1 3.2 subunit)
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Function
- pore-forming & voltage-sensitive alpha-1 subunit of voltage-sensitive Ca+2 channel
- alpha-1H gives rise to T-type Ca+2 currents
- T-type Ca+2 channels belong to the low-voltage activated (LVA) group
- strongly blocked by nickel & mibefradil
- a particularity of T-type Ca+2 channels is an opening at negative potentials, & a voltage-dependent inactivation
- T-type channels serve pacemaking functions in both central neurons & cardiac nodal cells
- role in Ca+2 signaling in secretory cells & vascular smooth muscle
- role in modulation of firing patterns of neurons during information processing
- role in cell growth processes
- T-type Ca+2 channels are activated by CaM-kinase III in response to increasing intracellular Ca+2
Structure
- each of the 4 internal repeats contains 5 hydrophobic transmembrane segments (S1, S2, S3, S5, S6) & one positively charged transmembrane segment (S4)
- S4 segments probably represent the voltage-sensor; they are characterized by a series of positively charged amino acids at every third position
- belongs to the Ca+2 channel alpha-1 subunit (TC 1.A.1.11) family
Compartment
membrane
Alternative splicing
named isoforms=2
Expression
Pathology
- defects in CACNA1H are a cause of: susceptibility to idiopathic generalized epilepsy type 6