Potassium channel subfamily K member 9

Potassium channel subfamily K member 9

K(+) channel that conducts voltage-dependent outward rectifying currents upon membrane depolarization. Voltage sensing is coupled to K(+) electrochemical gradient in an 'ion flux gating' mode where outward but not inward ion flow opens the gate11042359,11431495,26919430,38630723. Changes ion selectivity and becomes permeable to Na(+) ions in response to extracellular acidification. Protonation of the pH sensor His-98 stabilizes C-type inactivation conformation likely converting the channel from outward K(+)-conducting, to inward Na(+)-conducting to nonconductive state22948150,38630723. Homo- and heterodimerizes to form functional channels with distinct regulatory and gating properties (By similarity)23169818,38630723. Allows K(+) currents with fast-gating kinetics important for the repolarization and hyperpolarization phases of action potentials (By similarity). In granule neurons, hyperpolarizes the resting membrane potential to limit intrinsic neuronal excitability, but once the action potential threshold is reached, supports high-frequency action potential firing and increased neuronal excitability. Homomeric and/or heteromeric KCNK3:KCNK9 channels operate in cerebellar granule cells, whereas heteromeric KCNK1:KCNK9 enables currents in hippocampal dentate gyrus granule neurons (By similarity). Dispensable for central chemosensory respiration i.e. breathing controlled by brainstem CO2/pH, it rather conducts pH-sensitive currents and controls the firing rate of serotonergic raphe neurons involved in potentiation of the respiratory chemoreflex (By similarity). In retinal ganglion cells, mediates outward currents that regulate action potentials in response to acidification of the synaptic cleft. Involved in transmission of image-forming and nonimage-forming visual information in the retina (By similarity). In adrenal gland, contributes to the maintenance of a hyperpolarized resting membrane potential of aldosterone-producing cells at zona glomerulosa and limits aldosterone release as part of a regulatory mechanism that controls arterial blood pressure and electrolyte homeostasis (By similarity)

Quoted from UniProt’s FUNCTION annotation for Q9NPC2 (reviewed). The superscript numbers are UniProt’s own PubMed citations, kept in the sentence and in order, each linking to the paper it names.

What it acts with

STRING’s highest-confidence human functional partners. The combined score mixes several kinds of evidence, so each channel is shown separately — a partner supported by experiment is a different claim from one supported only by text mining, and for a receptor this is where its coupling appears as evidence rather than as assertion.

Where it sits in the cell

• Plasma membrane

Human Protein Atlas, by antibody immunofluorescence in cell lines — a different assay from the expression figures below, which are RNA.

UniProt, curated Cell membrane · Mitochondrion inner membrane · Cell projection, dendrite

Expression by cell type

Single cell type RNA, the 10 highest of those the Human Protein Atlas reports for this gene. Transcript, not protein, and a cell type rather than a tissue.

• Oocytes73.7 nCPM
• Adrenal medulla cells53.2 nCPM
• Brain excitatory neurons46 nCPM
• Thyrotrophs30.8 nCPM
• Retinal amacrine cells26.9 nCPM
• Other brain neurons15.1 nCPM
• Retinal horizontal cells14 nCPM
• Late spermatids13.5 nCPM
• Tuft cells11.5 nCPM
• Corticotrophs10.6 nCPM

Expression by tissue

The tissues this gene is enriched in, by consensus RNA. A tissue absent from this list is one the Atlas does not call specific for this gene, which is not the same as absent from it.

• brain7.4 nTPM