title: TRPV4 enhances the cellular uptake of aminoglycoside antibiotics.
abstract: The cochlea and kidney are susceptible to aminoglycoside-induced toxicity. The non-selective cation channel TRPV4 is expressed in kidney distal tubule cells, and hair cells and the stria vascularis in the inner ear. To determine whether TRPV4 is involved in aminoglycoside trafficking, we generated a murine proximal-tubule cell line (KPT2) and a distal-tubule cell line (KDT3). TRPV4 expression was confirmed in KDT3 cells but not in KPT2 cells. Removal of extracellular Ca(2+) significantly enhanced gentamicin-Texas-Red (GTTR) uptake by KDT3, indicative of permeation through non-selective cation channels. To determine whether TRPV4 is permeable to GTTR, stable cell lines were generated that express TRPV4 in KPT2 (KPT2-TRPV4). KPT2-TRPV4 cells took up more GTTR than control cell lines (KPT2-pBabe) in the absence of extracellular Ca(2+). TRPV4-dependent GTTR uptake was abolished by a point mutation within the crucial pore region of the channel, suggesting that GTTR permeates the TRPV4 channel. In an endolymph-like extracellular environment, clearance of GTTR was attenuated from KPT2-TRPV4 cells in a TRPV4-dependent fashion. We propose that TRPV4 has a role in aminoglycoside uptake and retention in the cochlea.
authors.affiliation: Oregon Hearing Research Center, Oregon Health and Science University, 3181 Sam Jackson Park Road, Portland, OR 97239, USA.
authors.forename: Takatoshi
authors.initials: T
authors.lastname: Karasawa
authors.forename: Qi
authors.initials: Q
authors.lastname: Wang
authors.forename: Yi
authors.initials: Y
authors.lastname: Fu
authors.forename: David M
authors.initials: DM
authors.lastname: Cohen
authors.forename: Peter S
authors.initials: PS
authors.lastname: Steyger
mesh_terms: D000617:Aminoglycosides / Q000378:metabolism*; D000818:Animals; D000900:Anti-Bacterial Agents / Q000378:metabolism*; D002118:Calcium / Q000494:pharmacology; D002460:Cell Line; D004285:Dogs; D007758:Ear, Inner / Q000166:cytology / Q000378:metabolism; D004710:Endolymph / Q000187:drug effects / Q000378:metabolism; D005110:Extracellular Space / Q000187:drug effects / Q000378:metabolism; D005839:Gentamicins / Q000378:metabolism; D007668:Kidney / Q000166:cytology / Q000378:metabolism; D008715:Methionine / Q000378:metabolism; D051379:Mice; D051381:Rats; D050916:TRPV Cation Channels / Q000378:metabolism*; D014966:Xanthenes / Q000378:metabolism
chemical_list: D000617:Aminoglycosides; D000900:Anti-Bacterial Agents; D005839:Gentamicins; D050916:TRPV Cation Channels; C486577:Trpv4 protein, rat; D014966:Xanthenes; C034657:Texas red; D008715:Methionine; D002118:Calcium