Figure 1: C-terminal cleavage by caspase 3 results in a distinctive PANX1 pore structure and maximum unitary conductance of ∼96 pS.
From: A quantized mechanism for activation of pannexin channels
(a) Electron micrograph and class-averaged EM images of negatively stained full-length (from 125 or 282 of 5,970 particles for the putative extracellular or cytoplasmic view, respectively) or caspase-cleaved PANX1 (from 79 or 56 of 6,892 particles); six-fold symmetry was imposed on the indicated images20. Schematics show the caspase cleavage site and expected cytoplasmic views of PANX1 hexameric channels, before and after cleavage. Scale bar, 50 nm; class-averaged image: 35.7 × 35.7 nm2. (b) Inside–out recordings from HEK293T cells expressing full-length PANX1-FLAG following membrane excision, and after exposure to activated caspase 3 (Casp3) and carbenoxolone (CBX, 50 μM). (c) Steady-state activity of caspase-activated, full-length PANX1-FLAG in an inside–out patch held at different potentials. C, closed state; O1 and O2, open-state amplitude for one and two channels. (d) Averaged single-channel current amplitudes at different patch potentials (± s.e.m., smaller than symbol size) reveal an outward-rectifying unitary conductance: 96.2±2.0 pS from +50 to +80 mV (n=5) and 12.2±0.2 pS from −80 to −50 mV (n=4). (e) Open probability of cleavage-activated PANX1-FLAG is independent of membrane voltage. Data from each patch is represented by a different colour.
