Imaging single-channel calcium microdomains

Abstract

The Ca 2+ microdomains generated around the mouth of open ion channels represent the basic building blocks from which cytosolic Ca 2+ signals are constructed. Recent improvements in optical imaging techniques now allow these microdomains to be visualized as single channel calcium fluorescence transients (SCCaFTs), providing information about channel properties that was previously accessible only by electrophysiological patch-clamp recordings. We review recent advances in single channel Ca 2+ imaging methodologies, with emphasis on total internal reflection fluorescence microscopy (TIRFM) as the technique of choice for recording SCCaFTs from voltageand ligand-gated plasmalemmal ion channels. This technique of 'optical patch-clamp recording' is massively parallel, permitting simultaneous imaging of hundreds of channels; provides millisecond resolution of gating kinetics together with sub-micron spatial resolution of channel locations; and is applicable to diverse families of membrane channels that display partial permeability to Ca 2+ ions.

Actin-based confinement of calcium responses during Shigella invasion

“…1c-e). Remarkably, when cells were treated with the Ca 2 þ chelator BAPTA-AM, known to inhibit global as well as local Ca 2 þ responses 20,21 , the average frequency of actin foci per cell decreased significantly, with only 3 ± 1.6% observed when compared with control untreated cells ( Supplementary Fig. S6).…”

“…Although global Ca 2 þ responses may have long-term consequences by activating gene transcription, local Ca 2 þ signals, evoked by weak InsP 3 stimuli, can occur independently of global Ca 2 þ increases. These Ca 2 þ signals, confined in a small cytoplasmic region around the Ca 2 þ -releasing sites 20 , correspond to elementary events of Ca 2 þ release from discrete clusters of channels from intracellular pools 21 . Local Ca 2 þ signals occuring within the vicinity of the plasma membrane could directly regulate Ca 2 þ -dependent processes, including processes involving cortical actin reorganization.…”

Mid-range Ca2+ signalling mediated by functional coupling between store-operated Ca2+ entry and IP3-dependent Ca2+ release

“…Theoretical calculations argue that this point-source Ca 2 þ rise decays rapidly in the spatial dimension due to Ca 2 þ buffering resulting in a spatial spread estimated to be on the order of 20 nm (refs 7,8). In addition, Ca 2 þ concentrations fall rapidly in the sub-micromolar range within 200 nm of the channel due to Ca 2 þ buffering 7,9,10 . Experimental approaches have been developed to estimate the amplitude and spatial spread of microdomain Ca 2 þ transients, including endogenous biological Ca 2 þ sensors such as vesicle exocytosis and Ca 2 þ -activated K þ channels 11,12 , and optical single-channel imaging approaches using total internal reflection fluorescence (TIRF) and confocal microscopy 9 .…”

State of Art on Bioimaging by Nanoparticles in Hyperthermia and Thermometry: Visualization of Tissue Protein Targeting

“…The relationship was based on temperature dependence of the proton chemical shift of water < 0.01 ppm/ºC at < 0.7 Hz at 1.5T for 1 ºC temperature change using lanthanide complexes [141]. [142][143][144][145].…”