Pendrin (encoded by Pds, Slc26a4) is a Cl−/HCO3− exchanger expressed in the apical regions of type B and non-A, non-B intercalated cells of kidney and mediates renal Cl− absorption, particularly when upregulated. Aldosterone increases blood pressure by increasing absorption of both Na+ and Cl− through increased protein abundance and function of Na+ transporters, such as the epithelial Na+ channel (ENaC) and the Na+-Cl− cotransporter (NCC), as well as Cl− transporters, such as pendrin. Because aldosterone analogs do not increase blood pressure in Slc26a4−/− mice, we asked whether Na+ excretion and Na+ transporter protein abundance are altered in kidneys from these mutant mice. Thus wild-type and Slc26a4-null mice were given a NaCl-replete, a NaCl-restricted, or NaCl-replete diet and aldosterone or aldosterone analogs. Abundance of the major renal Na+ transporters was examined with immunoblots and immunohistochemistry. Slc26a4-null mice showed an impaired ability to conserve Na+ during dietary NaCl restriction. Under treatment conditions in which circulating aldosterone is increased, α-, β-, and 85-kDa γ-ENaC subunit protein abundances were reduced 15–35%, whereas abundance of the 70-kDa fragment of γ-ENaC was reduced ∼70% in Slc26a4-null relative to wild-type mice. Moreover, ENaC-dependent changes in transepithelial voltage were much lower in cortical collecting ducts from Slc26a4-null than from wild-type mice. Thus, in kidney, ENaC protein abundance and function are modulated by pendrin or through a pendrin-dependent downstream event. The reduced ENaC protein abundance and function observed in Slc26a4-null mice contribute to their lower blood pressure and reduced ability to conserve Na+ during NaCl restriction.

The epithelial Na ϩ channel, ENaC, and the Cl Ϫ /HCO 3 Ϫ exchanger, pendrin, mediate NaCl absorption within the cortical collecting duct and the connecting tubule. Although pendrin and ENaC localize to different cell types, ENaC subunit abundance and activity are lower in aldosterone-treated pendrin-null mice relative to wild-type mice. Because pendrin mediates HCO 3 Ϫ secretion, we asked if increasing distal delivery of HCO 3 Ϫ through a pendrin-independent mechanism "rescues" ENaC function in pen- 21: 192821: -194121: , 201021: . doi: 10.1681 Pendrin, encoded by Slc26a4, is an aldosterone-sensitive Cl Ϫ /HCO 3 Ϫ exchanger that mediates Cl Ϫ absorption and HCO 3 Ϫ secretion in the cortical collecting duct (CCD). 1-3 During NaCl restriction, pendrin-null mice excrete more NaCl than wild-type mice, which increases apparent vascular volume contraction and lowers BP. [3][4][5] The chloruresis observed in pendrin-null mice during NaCl restriction likely results from the absence of pendrin-mediated Cl Ϫ absorption. 3,4 However, because pendrin does not transport Na ϩ , the cause of the natriuresis observed in the mutant mice was explored further. After either dietary NaCl restriction or the administration of aldosterone, renal ENaC function and ENaC subunit abundance were lower in pendrin-null mice than in wildtype mice. 5 In particular, ␥ ENaC abundance was reduced in kidneys from pendrin-null mice relative to wild-type mice. However, how pendrin J Am Soc Nephrol

Hippocampal alpha-calcium/calmodulin-dependent protein kinase II (alphaCaMKII) has been implicated in neuronal plasticity and spatial learning. In the present experiment, an adeno-associated virus (AAV) vector was designed to express alphaCaMKII driven by the U6 promotor. Microinfusion of this vector into the rat hippocampus increased alphaCaMKII immunoreactivity by approximately 73% (Western analysis) and improved performance in a water maze task. Locomotor activity and exploratory behavior in an open field task were not altered by the overexpression of alphaCaMKII. These data support a role for alphaCaMKII in spatial or explicit memory storage. The advantages of viral vectors for manipulating target proteins expression compared with genetically modified mouse models are discussed.

Background Exposure to chronic ethanol results in changes in expression of proteins that regulate neuronal excitability. The present study examined whether chronic ethanol alters the hippocampal expression and function of Fragile-X mental retardation protein (FMRP), and the role of FMRP in the modulation of chronic ethanol-induced changes in expression of NMDA receptors and Kv4.2 channels. Methods For in-vivo studies, C57Bl6/J mice underwent a chronic intermittent ethanol (CIE) vapor exposure procedure. After CIE, hippocampal tissue was collected and subjected to immunoblot blot analysis of NMDA receptor subunits (GluN1, GluN2B), Kv4.2 and its accessory protein KChIP3. For in-vitro studies, hippocampal slice cultures were exposed to 75 mM ethanol for 8 days. Following ethanol exposure, mRNAs bound to FMRP was measured. In a separate set of studies, cultures were exposed to an inhibitor of S6K1 (PF-4708671, 6 μM) in order to assess whether ethanol-induced homeostatic changes in protein expression depend upon changes in FMRP activity. Results Immunoblot blot analysis revealed increases in GluN1 and GluN2B but reductions in Kv4.2 and KChIP3. Analysis of mRNAs bound to FMRP revealed a similar bidirectional change observed as reduction of GluN2B and increase in Kv4.2 and KChiP3 mRNA transcripts. Analysis of FMRP further revealed that while chronic ethanol did not alter the expression of FMRP, it significantly increased phosphorylation of FMRP at the S499 residue that is known to critically regulate its activity. Inhibition of S6K1 prevented the chronic ethanol-induced increase in phospho-FMRP and changes in NMDA subunits, Kv4.2 and KChiP3. In contrast, PF-4708671 had no effect in the absence of alcohol, indicating it was specific for the chronic ethanol-induce changes. Conclusions These findings demonstrate that chronic ethanol exposure enhances translational control of plasticity related proteins by FMRP, and that S6K1 and FMRP activity are required for expression of chronic ethanol-induced homeostatic plasticity at glutamatergic synapses in the hippocampus.

Rationale Chronic alcohol-induced cognitive impairments and maladaptive plasticity of glutamatergic synapses are well-documented. However, it is unknown if prolonged alcohol exposure affects dendritic signaling that may underlie hippocampal dysfunction in alcoholics. Back-propagation of action potentials (bAPs) into apical dendrites of hippocampal neurons provides distance-dependent signals that modulate dendritic and synaptic plasticity. The amplitude of bAPs decreases with distance from the soma that is thought to reflect an increase in the density of Kv4.2 channels toward distal dendrites. Objective The aim of this study was to quantify changes in hippocampal Kv4.2 channel function and expression using electrophysiology, Ca2+ imaging, and western blot analyses in a well-characterized in-vitro model of chronic alcohol exposure. Results Chronic alcohol exposure significantly decreased expression of Kv4.2 channels and KChIP3 in hippocampus. This reduction was associated with an attenuation of macroscopic A-type K+ currents in CA1 neurons. Chronic alcohol exposure increased bAP-evoked Ca2+ transients in the distal apical dendrites of CA1 pyramidal neurons. The enhanced bAP-evoked Ca2+ transients induced by chronic alcohol exposure were not related to alteration of synaptic targeting of NMDA receptors or morphological adaptations in apical dendritic arborization. Conclusions These data suggest that chronic alcohol-induced decreases in Kv4.2 channel function possibly mediated by a down-regulation of KChIP3, drive the elevated bAP-associated Ca2+ transients in distal apical dendrites. Alcohol-induced enhancement of bAPs may affect metaplasticity and signal integration in apical dendrites of hippocampal neurons leading to alterations in hippocampal function.