Ion channel that contributes to passive transmembrane potassium transport and to the regulation of the resting membrane potential in brain astrocytes, but also in kidney and in other tissues (PubMed:17452494, PubMed:19571146). Forms dimeric channels through which potassium ions pass in accordance with their electrochemical gradient. The channel is selective for K(+) ions at physiological potassium concentrations and at neutral pH, but becomes permeable to Na(+) at subphysiological K(+) levels and upon acidification of the extracellular medium (PubMed:22948150). The homodimer has very low potassium channel activity, when expressed in heterologous systems, and can function as weakly inward rectifying potassium channel. Channel activity is modulated by activation of serotonin receptors (PubMed:17452494). Heterodimeric channels containing KCNK1 and KCNK2 have much higher activity, and may represent the predominant form in astrocytes (By similarity). Heterodimeric channels containing KCNK1 and KCNK3 or KCNK9 have much higher activity. Heterodimeric channels formed by KCNK1 and KCNK9 may contribute to halothane-sensitive currents (By similarity). Mediates outward rectifying potassium currents in dentate gyrus granule cells and contributes to the regulation of their resting membrane potential (By similarity). Contributes to the regulation of action potential firing in dentate gyrus granule cells and down-regulates their intrinsic excitability (By similarity). Contributes to the regulation of the resting membrane potential of pancreatic beta cells (By similarity). In astrocytes, the heterodimer formed by KCNK1 and KCNK2 is required for rapid glutamate release in response to activation of G-protein coupled receptors, such as F2R and CNR1 (By similarity). Required for normal ion and water transport in the kidney (By similarity). The low channel activity of homodimeric KCNK1 may be due to sumoylation. The low channel activity may be due to rapid internalization from the cell membrane and retention in recycling endosomes (By similarity). Inhibited by 100 uM quinine. Slightly inhibited by Ba(+) (PubMed:17452494). Activity is first increased and then decreased when the extracellular pH is lowered to 6.0 (PubMed:17452494, PubMed:22948150). Both activation and channel closure are very rapid. Is not voltage-gated (PubMed:19571146). The relationship between voltage and current is nearly linear (PubMed:19571146). Homodimer; disulfide-linked (PubMed:9843722). Heterodimer with KCNK2; disulfide-linked (By similarity). In astrocytes, forms mostly heterodimeric potassium channels with KCNK2, with only a minor proportion of functional channels containing homodimeric KCNK1 (By similarity). Interacts with KCNK3 and KCNK9, forming functional heterodimeric channels (By similarity). Interacts with GNG4 (By similarity). Identified in a complex with PSD and ARF6; interacts only with PSD that is bound to ARF6 (By similarity). Interacts with UBE2I (By similarity). The heterodimer with KCNK2 is detected at the astrocyte cell membrane. Not detected at the astrocyte cell membrane when KCNK2 is absent. Detected on neuronal cell bodies, and to a lesser degree on neuronal cell projections (By similarity). Detected in synaptic membranes (PubMed:9843722). Detected at the apical cell membrane in stria vascularis in the cochlea (PubMed:12855359). Detected on hippocampus dentate gyrus granule cell bodies and to a lesser degree on proximal dendrites. Detected at the apical cell membrane of vestibular dark cells situated between the crista and the utricle in the inner ear. Detected at the apical cell membrane in kidney proximal tubule segment S1 and in subapical compartments in segments S1, S2 and S3 (PubMed:9843722). Predominantly in cytoplasmic structures in kidney distal convoluted tubules and collecting ducts (By similarity). Detected at the apical cell membrane of bronchial epithelial cells (By similarity). Detected in brain and in kidney cortex and medulla, especially at the renal brush border membranes of the proximal convoluted tubules, in distal tubules and on intercalated cells of the collecting duct (PubMed:9843722). Detected cerebellum granule neurons (PubMed:25305496). Detected in astrocytes in hippocampus stratum radiatum (PubMed:19571146). Highly expressed in the stria vascularis in the cochlea (PubMed:12855359). Detected in neurons in Scarpa's ganglion in the inner ear, at nerve terminals in the crista ampullaris, in supporting cells and dark cells, but not in hair cells (PubMed:18838117) (at protein level). Detected in the brain cerebellar granule cell layer, amygdala, thalamus reticular nucleus, habenula, mesencephalic trigeminal neurons, neocortex and piriform cortex, and at lower levels in the olfactory bulb (PubMed:11567039). Detected cerebellum granule neurons (PubMed:23169818, PubMed:25305496). Detected in Scarpa's ganglia and crista ampullaris in the inner ear (PubMed:18838117). Sumoylation is controversial. Sumoylated by UBE2I. Not sumoylated when expressed in xenopus oocytes or mammalian cells. Sumoylation inactivates the channel, but does not interfere with expression at the cell membrane. Sumoylation of a single subunit is sufficient to silence the dimeric channel. Sumoylation of KCNK1 is sufficient to silence heterodimeric channels formed by KCNK1 and KCNK3 or KCNK9. Desumoylated by SENP1; this activates the channel. Desumoylated by SENP1; this strongly increases halothane-mediated activation of heterodimeric channels formed with KCNK9. SENP1 treatment has no effect. When the external pH is lowered, it takes about 8 minutes till the channel has reached a new, stable state characterized by increased Na(+) permeability. Likewise, when raising the pH back to 7.4, it takes about 12 minutes for the channel to regain its original selectivity for K(+). Belongs to the two pore domain potassium channel (TC 1.A.1.8) family.