title: siRNA knock-down of gamma-glutamyl transpeptidase does not affect hypoxic K+ channel inhibition.
abstract: Large conductance, Ca(2+)-sensitive potassium (BK) channels are critical components of the O(2) signalling cascade in a number of cells, including the carotid body and central neurones. Although the nature of the BK channel O(2) sensor is still unknown, evidence suggests redox modulators might form part of the O(2) sensing channel complex. By metabolising glutathione, gamma-glutamyl transpeptidase (gammaGT) could act as such an O(2) sensor. Western blotting and immunocytochemistry revealed high gammaGT expression in HEK293 cells expressing the alpha- and beta-subunits of human recombinant BK and gammaGT co-immunoprecipitated with BKalpha. Acivicin blockade of gammaGT reversibly inhibited BK channels, suggesting that this BKalpha protein partner contributes to tonic channel activity. However, knock-out of gammaGT using siRNA had no effect on hypoxic BK channel inhibition. Together, these data indicate that gammaGT is a BKalpha protein partner, that its activity regulates BK channels but that it is not the BK O(2) sensor.
authors.affiliation: School of Biomedical Sciences, University of Leeds, UK.
authors.forename: Sandile E
authors.initials: SE
authors.lastname: Williams
authors.forename: Phillippa
authors.initials: P
authors.lastname: Wootton
authors.forename: Helen S
authors.initials: HS
authors.lastname: Mason
authors.forename: David E
authors.initials: DE
authors.lastname: Iles
authors.forename: C
authors.initials: C
authors.lastname: Peers
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Kemp
mesh_terms: D015687:Cell Hypoxia / Q000187:drug effects / Q000502:physiology*; D002460:Cell Line; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology; D020868:Gene Silencing / Q000502:physiology; D006801:Humans; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology; D007555:Isoxazoles / Q000494:pharmacology*; D007668:Kidney / Q000187:drug effects* / Q000196:embryology / Q000502:physiology*; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits; D051036:Large-Conductance Calcium-Activated Potassium Channels; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D010100:Oxygen / Q000378:metabolism; D024681:Potassium Channels, Calcium-Activated / Q000037:antagonists & inhibitors* / Q000502:physiology*; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D005723:gamma-Glutamyltransferase / Q000235:genetics / Q000378:metabolism*
chemical_list: D007555:Isoxazoles; C494841:KCNMA1 protein, human; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits; D051036:Large-Conductance Calcium-Activated Potassium Channels; D024681:Potassium Channels, Calcium-Activated; D034741:RNA, Small Interfering; D005723:gamma-Glutamyltransferase; C006303:acivicin; D010100:Oxygen