ThermoTRP channels (thermoTRPs) define a subfamily of the transient receptor potential (TRP) channels that are activated by changes in the environmental temperature, from noxious cold to injurious heat. Acting as integrators of several stimuli and signalling pathways, dysfunction of these channels contributes to several pathological states. The surface expression of thermoTRPs is controlled by both, the constitutive and regulated vesicular trafficking. Modulation of receptor surface density during pathological processes is nowadays considered as an interesting therapeutic approach for management of diseases, such as chronic pain, in which an increased trafficking is associated with the pathological state. This review will focus on the recent advances trafficking of the thermoTRP channels, TRPV1, TRPV2, TRPV4, TRPM3, TRPM8 and TRPA1, into/from the plasma membrane. Particularly, regulated membrane insertion of thermoTRPs channels contributes to a fine tuning of final channel activity, and indeed, it has resulted in the development of novel therapeutic approaches with successful clinical results such as disruption of SNARE-dependent exocytosis by botulinum toxin or botulinomimetic peptides.
We investigated the temporal and spatial expression of SK2 in the developing mouse hippocampus using molecular and biochemical techniques, quantitative immunogold electron microscopy, and electrophysiology. The mRNA encoding SK2 was expressed in the developing and adult hippocampus. Western blotting and immunohistochemistry showed that SK2 protein increased with age. This was accompanied by a shift in subcellular localization. Early in development (P5), SK2 was predominantly localized to the endoplasmic reticulum in the pyramidal cell layer. But by P30 SK2 was almost exclusively expressed in the dendrites and spines. The level of SK2 at the postsynaptic density (PSD) also increased during development. In the adult, SK2 expression on the spine plasma membrane showed a proximal-to-distal gradient. Consistent with this redistribution and gradient of SK2, the selective SK channel blocker apamin increased evoked excitatory postsynaptic potentials (EPSPs) only in CA1 pyramidal neurons from mice older than P15. However, the effect of apamin on EPSPs was not different between synapses in proximal or distal stratum radiatum or stratum lacunosum-moleculare in adult. These results show a developmental increase and gradient in SK2-containing channel surface expression that underlie their influence on neurotransmission, and that may contribute to increased memory acquisition during early development.
Ca(2+) channel ? subunits determine the maturation, biophysical properties and cell surface expression of high voltage-activated channels. Thus, we have analysed the expression, regional distribution and subcellular localization of the Ca(v) ? subunit family in mice from birth to adulthood. In the hippocampus and cerebellum, Ca(v) ?(1), Ca(v) ?(3) and Ca(v) ?(4) protein levels increased with age, although there were marked region- and developmental stage-specific differences in their expression. Ca(v) ?(1) was predominantly expressed in the strata oriens and radiatum of the hippocampus, and only weakly in the cerebellum. The Ca(v) ?(3) subunit was mainly expressed in the strata radiatum and lucidum of the hippocampus and in the molecular layer of the cerebellum. During development, Ca(v) ?(3) protein expression in the cerebellum peaked at postnatal days (P) 15 and 21, and had diminished drastically by P60, and in the hippocampus increased with age throughout all subfields. Ca(v) ?(4) protein was detected throughout the cerebellum, particularly in the molecular layer, and in contrast to the other subunits, Ca(v) ?(4) was mainly detected in the molecular layer and the hilus of the hippocampus. At the subcellular level, Ca(v) ?(1) and Ca(v) ?(3) were predominantly located post-synaptically in hippocampal pyramidal cells and cerebellar Purkinje cells. Ca(v) ?(4) subunits were detected in the pre-synaptic and post-synaptic compartments of both regions, albeit more strongly at post-synaptic sites. These results shed new light on the developmental regulation and subcellular localization of Ca(v) ? subunits, and their possible role in pre- and post-synaptic transmission.
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