NCBI Summary:
Potassium channels are present in most mammalian cells, where they participate in a wide range of physiologic responses. The protein encoded by this gene is an integral membrane protein and inward-rectifier type potassium channel. The encoded protein, which has a greater tendency to allow potassium to flow into a cell rather than out of a cell, is controlled by G-proteins. It may associate with two other G-protein-activated potassium channels to form a heteromultimeric pore-forming complex.
General function
Channel/transport protein
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Cellular localization
Plasma membrane
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Ovarian function
Comment
Expression regulated by
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Ovarian localization
Granulosa, Luteal cells
Comment
THE KATP CHANNEL IN ENDOCRINE CELLS OF THE HUMAN OVARY: ROLE IN MEMBRANE POTENTIAL GENERATION AND STEROIDOGENESIS. Kunz L et al. Context: KATP channels couple the metabolic state with the membrane potential in several cell types and, recently, evidence for KATP channels was given in rat Corpus luteum, a fast growing and metabolically highly active tissue. Objective: We studied whether KATP channels are present in the human ovary and in luteinized granulosa cells (GCs). Human GCs were examined regarding functionality and physiological role of the channel. Patients and Intervention: Human GCs were obtained from in vitro-fertilization patients. Results: KATP channels are involved in membrane potential generation in human GCs since application of the KATP blocker glibenclamide resulted in depolarization as monitored by fluorescence microscopy. Furthermore, glibenclamide significantly attenuated human chorionic gonadotropin-induced progesterone production. The channel pore is composed of Kir6.1, but not of Kir6.2 as indicated by RT-PCR. Kir6.1 subunit protein was detected in human follicular and luteal cells by immunohistochemistry and localized to the plasma membrane of human GCs by immunogold-staining. RT-PCR experiments revealed the sulfonylurea receptor subunit SUR2B as part of the KATP channel. In addition, mRNAs encoding SUR1 and SUR2A were detected in some preparations. There is no evidence for mitochondrial KATP channels in human GCs since we detected neither Kir6.1 protein in mitochondrial membranes nor alterations of mitochondrial membrane potential by glibenclamide or the KATP opener diazoxide. Conclusions: Endocrine cells of the human ovary possess functional KATP channels, which are linked to both plasma membrane potential generation and progesterone production. Our results may provide new insights into human ovarian physiology and raise the possibility of pharmacological targeting.