title: Single-channel properties of a stretch-sensitive chloride channel in the human mast cell line HMC-1.
abstract: A stretch-activated (SA) Cl(-) channel in the plasma membrane of the human mast cell line HMC-1 was identified in outside-out patch-clamp experiments. SA currents, induced by pressure applied to the pipette, exhibited voltage dependence with strong outward rectification (55.1 pS at +100 mV and an about tenfold lower conductance at -100 mV). The probability of the SA channel being open (P (o)) also showed steep outward rectification and pressure dependence. The open-time distribution was fitted with three components with time constants of tau(1o) = 755.1 ms, tau(2o) = 166.4 ms, and tau(3o) = 16.5 ms at +60 mV. The closed-time distribution also required three components with time constants of tau(1c) = 661.6 ms, tau(2c) = 253.2 ms, and tau(3c) = 5.6 ms at +60 mV. Lowering extracellular Cl(-) concentration reduced the conductance, shifted the reversal potential toward chloride reversal potential, and decreased the P (o) at positive potentials. The SA Cl(-) currents were reversibly blocked by the chloride channel blocker 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS) but not by (Z)-1-(p-dimethylaminoethoxyphenyl)-1,2-diphenyl-1-butene (tamoxifen). Furthermore, in HMC-1 cells swelling due to osmotic stress, DIDS could inhibit the increase in intracellular [Ca(2+)] and degranulation. We conclude that in the HMC-1 cell line, the SA outward currents are mediated by Cl(-) influx. The SA Cl(-) channel might contribute to mast cell degranulation caused by mechanical stimuli or accelerate membrane fusion during the degranulation process.
authors.affiliation: Shanghai Research Center for Acupuncture and Meridians, Department of Mechanics and Engineering Science, Fudan University, 220 Handan Rd, Shanghai, 200433, China.
authors.forename: Lina
authors.initials: L
authors.lastname: Wang
authors.forename: Guanghong
authors.initials: G
authors.lastname: Ding
authors.forename: Quanbao
authors.initials: Q
authors.lastname: Gu
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Schwarz
mesh_terms: D002460:Cell Line; D018118:Chloride Channels / Q000502:physiology*; D055119:Elastic Modulus; D006801:Humans; D015640:Ion Channel Gating / Q000502:physiology*; D008407:Mast Cells / Q000502:physiology*; D040542:Mechanotransduction, Cellular / Q000502:physiology*; D008564:Membrane Potentials / Q000502:physiology*; D011312:Pressure
chemical_list: D018118:Chloride Channels