Anti-GAPDH Antibody [1D4] (A85382)

Alpha7 nicotinic acetylcholine receptors (a7-nAChRs) are ionotropic, Ca²⁺-permeable receptors highly expressed in brain regions involved in memory formation, such as the hippocampus. Their activation induces cation influx and neuronal depolarization, which in turn promotes glutamate release-highlighting a crucial interplay between cholinergic and glutamatergic signaling in the healthy brain. Interestingly, the genetic deletion of a7-nAChRs in mice (a7-KO mice) leads to an Alzheimer's disease (AD)-like phenotype characterized by aberrant amyloid-ß accumulation, tau phosphorylation, and neuroinflammation in aged (>12 months) mice. However, glutamatergic transmission in these mice prior to the onset of the AD-like phenotype has been poorly investigated. We thus studied molecular and functional properties of glutamatergic transmission in 4-6-months-old a7-KO mice, representing a prodromal phase of the AD-like neuropathology. We found that hippocampal CA1 neurons in brain slices from a7-KO mice showed a reduced frequency of the spontaneous excitatory post-synaptic currents (sEPSCs) compared to those of wild-type (WT) mice. On the contrary, the amplitude of sEPSCs was not affected, although in a7-KO neurons these currents displayed a longer rise time than in wild-type. CA1 neurons from a7-KO mice also exhibited a significantly smaller evoked NMDA currents than WT neurons, whereas AMPA currents were unaffected. From a molecular point of view, hippocampal neurons of a7-KO mice exhibited an increased expression of the pre-synaptic protein Synapsin-1 and of the NMDA subunits GluN2A and GluN2B, but no modifications in the expression of AMPA receptor subunits (GluA1 and GluA2) were found. Importantly, selective re-expression of the a7-nAChRs in neurons of a7-KO mice restored the evoked NMDA current amplitude and the rise time of sEPSCs, but it did not rescue the frequency of sEPSCs, thus suggesting that post-synaptic integrity depends on neuronal a7-nAChRs.

K_V7.4 channels are important regulators of membrane potential and excitability in multiple tissues and are emerging as key effectors of steroid hormone signaling. Here, 17ß-estradiol (E2) was examined as a modulator of recombinant K_V7.4 channels expressed in HEK293 cells. Whole-cell patch-clamp recordings showed that acute application of E2 reduced K_V7.4 current density. At nanomolar concentrations, both E2 and the alternate GPER1 agonist aldosterone inhibited K_V7.4 currents only when G protein-coupled estrogen receptor 1 (GPER1) was co-expressed, indicating a receptor-dependent mechanism. Pharmacological inhibition showed that phospholipase C (PLC) and protein kinase C (PKC), but not adenylyl cyclase, contribute to GPER1-mediated inhibition of K_V7.4. In contrast, equivalent experiments performed with K_V7.5 channels showed no significant effect of E2 despite GPER1 co-expression, suggesting subtype-selective regulation within the K_V7 family. Surface biotinylation experiments suggest that GPER1 co-expression reduced surface K_V7.4 expression, with a further reduction observed following E2 treatment. Finally, both E2 and aldosterone negatively regulate the sensitivity of K_V7.2-5 activator ML213-mediated relaxation in arteries from female rats. Together, these findings identify K_V7.4 as a downstream effector of rapid GPER1-dependent estrogen signaling and suggest that steroid status may influence K_V7-targeted therapeutic responses.