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. 2010 Apr 16;213(9):1417–1424. doi: 10.1242/jeb.037234

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Fig. 1. — The lobster sodium-gated cation (SGC) channel can be activated and modulated by exogenous lipids in inside-out membrane patches. (A) Current traces of a channel activated by exogenous phosphatidylinositol 3,4,5-trisphosphate [PI(3,4,5)P3, 16 μmol l⁻¹]. Holding potential, −70 mV. Electrode solution: NaCl (210 mmol l⁻¹) + Ca²⁺ (10 nmol l⁻¹). Bar above current traces shows time course of solution application. LiCl: LiCl (210 mmol l⁻¹) + Ca²⁺ (10 nmol l⁻¹). NaCl: NaCl (210 mmol l⁻¹) + Ca²⁺ (10 nmol l⁻¹). Na⁺+Ca²⁺: NaCl (210 mmol l⁻¹) + Ca²⁺ (100 μmol l⁻¹). Note: exogenous PI(3,4,5)P3 (1,2-dipalmitoyl analog was used in the experiment) activates the channel independently of intracellular sodium and calcium. Both current traces are gap-free recordings from the same patch. (B) Multi-channel activity in another patch exposed to Na⁺+Ca²⁺ and different PIs (20 μmol l⁻¹) in the presence of 180 mmol l⁻¹ Li⁺ and 30 mmol l⁻¹ Na⁺ (Li⁺+Na⁺). Holding potential, −60 mV. Electrode solution: NaCl (210 mmol l⁻¹) + Ca²⁺ (10 nmol l⁻¹). Bar above current traces shows time course of solution application. Note: PI(3,4,5)P3 greatly increased the channel open probability in the presence of 30 mmol l⁻¹ Na⁺ whereas phosphatidylinositol (PI), PI(3)P and PI(4)P were ineffective. (C) Bar diagram of the relative efficacy of various PIs, a diacylglycerol (DAG) analog and inositol phosphates (IPs) on the SGC channel in membrane patches excised from cultured lobster olfactory receptor neurons (ORNs). Efficacy was calculated as (NP_o–NP_oc)/NP_oc, where N is the number of channels, P_oc is the channel open probability in control conditions (Li⁺+Na⁺) and P_o is the channel open probability in Li⁺+Na⁺ and 20 μmol l⁻¹ of one of the following: PI (n=5), PI(3)P (n=5), PI(4)P (n=5), PI(5)P (n=4), PI(4,5)P2 (n=4), PI(3,5)P2 (n=4), PI(3,4)P2 (n=3), PI(3,4,5)P3 (n=9) or 1-oleoyl-2-acetyl-sn-glycerol (DAG analog, 10 μmol l⁻¹, n=7), IP3 (3–10 μmol l⁻¹, n=8), IP4 (5–20 μmol l⁻¹, n=15) and IP5 (10 μmol l⁻¹, n=5). Note: PI(3,4,5)P3 is the most effective lipid.