voltage-dependent Ca+2 channel alpha-1i (T-type, Cav3.3, CACNA1I, KIAA1120)

Function

• pore-forming & voltage-sensitive alpha-1 subunit of voltage-sensitive Ca+2 channel
• alpha-1I 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
• gates in voltage ranges similar to, but higher than alpha-1G or alpha-1H (putative)
• interacts with CATSPER1 & CATSPER2, leading to suppress T-type Ca+2 channel activity

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=4

Expression

brain specific

More general terms

• voltage-dependent Ca+2 channel alpha-1

Component of

• T-type Ca+2 channel or transient current Ca+2 channel

Database

• Entrez gene: http://www.ncbi.nlm.nih.gov/sites/entrez?db=gene&cmd=Retrieve&dopt=Graphics&list_uids=8911
• Kegg: http://www.genome.jp/dbget-bin/www_bget?hsa:8911
• OMIM: https://mirror.omim.org/entry/608230
• UniProt: http://www.uniprot.org/uniprot/Q9P0X4.html