- Peptide (C)RLDAHLYWSIPSRLDEKV, corresponding to residues 344-361 of rat KCNJ9 (Accession Q63511). Intracellular, C-terminus.
- Rat brain membranes (1:200).
- Western blot analysis of rat brain membranes:1. Anti-GIRK3 (Kir3.3) Antibody (#APC-038), (1:200).
2. Anti-GIRK3 (Kir3.3) Antibody, preincubated with GIRK3/Kir3.3 Blocking Peptide (#BLP-PC038).
- Rat brain sections.
- Mouse INS-IE cells (Iwanir, S. and Reuveny, E. (2008) Pflugers Arch. 456, 1097.).
Kir3.3 (or G-protein regulated Inward-Rectifier K+ channel, GIRK3) is a member of the family of inward rectifying K+ channels. The family includes 15 members that are structurally and functionally different from the voltage-dependent K+ channels.
The family’s topology consists of two transmembrane domains that flank a single and highly conserved pore region with intracellular N- and C-termini. As is the case for the voltage-dependent K+ channels the functional unit for the Kir channels is composed of four subunit that can assembly as either homo or heterotetramers.
Kir channels are characterized by a K+ efflux that is limited by depolarizing membrane potentials thus making them essential for controlling resting membrane potential and K+ homeostasis.
Kir3.3 is a member of the Kir3.x subfamily that includes four members (Kir3.1- Kir3.4). The Kir3 family is characterized by the fact that the channels can be activated by neurotransmitters and other factors acting via the activation of G-protein coupled receptors. Binding of the corresponding ligand to the G-protein receptor induces the dissociation of Ga-GTP from the Gbg dimer. The latter directly binds to Kir3 and activates the channel.1,2
Kir3.3 is mainly expressed in the brain, were it co-assembles with Kir3.1 or Kir3.2. The functional impact of Kir3.3 is less well understood than the other Kir3 channels. However, heteromers composed of Kir3.2 and Kir3.3 were found to be primarily responsible for the opioid-induced current and hyperpolarization observed in mouse locus ceruleus (LC) neurons.3