Primary cilia TRP channel regulates hippocampal excitability.

Polycystins (PKD2, PKD2L1, and PKD2L2) are members of the transient receptor potential family, which form ciliary ion channels. Most notably, PKD2 dysregulation in the kidney nephron cilia is associated with polycystic kidney disease, but the function of PKD2L1 in neurons is undefined. In this report, we develop animal models to track the expression and subcellular localization of PKD2L1 in the brain.

Energetic landscape of polycystin channel gating.

Members of the polycystin family (PKD2 and PKD2L1) of transient receptor potential (TRP) channels conduct Ca and depolarizing monovalent cations. Variants in PKD2 cause autosomal dominant polycystic kidney disease (ADPKD) in humans, whereas loss of PKD2L1 expression causes seizure susceptibility in mice. Understanding structural and functional regulation of these channels will provide the basis for interpreting their molecular dysregulation in disease states.

Targeting the tamoxifen receptor within sodium channels to block osteoarthritic pain.

Voltage-gated sodium channels (Na) in nociceptive neurons initiate action potentials required for transmission of aberrant painful stimuli observed in osteoarthritis (OA). Targeting Na subtypes with drugs to produce analgesic effects for OA pain management is a developing therapeutic area. Previously, we determined the receptor site for the tamoxifen analog N-desmethyltamoxifen (ND-Tam) within a prokaryotic Na.

Preventing Phosphorylation of the GABA R β3 Subunit Compromises the Behavioral Effects of Neuroactive Steroids.

Neuroactive steroids (NASs) have potent anxiolytic, anticonvulsant, sedative, and hypnotic actions, that reflect in part their efficacy as GABA R positive allosteric modulators (PAM). In addition to this, NAS exert metabotropic effects on GABAergic inhibition the activation of membrane progesterone receptors (mPRs), which are G-protein coupled receptors. mPR activation enhances the phosphorylation of residues serine 408 and 409 (S408/9) in the β3 subunit of GABA Rs, increasing their accumulation in the plasma membrane leading to a sustained increase in tonic inhibition.

Disrupting polycystin-2 EF hand Ca affinity does not alter channel function or contribute to polycystic kidney disease.

Approximately 15% of autosomal dominant polycystic kidney disease (ADPKD) is caused by variants in encodes polycystin-2, which forms an ion channel in primary cilia and endoplasmic reticulum (ER) membranes of renal collecting duct cells. Elevated internal Ca modulates polycystin-2 voltage-dependent gating and subsequent desensitization - two biophysical regulatory mechanisms that control its function at physiological membrane potentials. Here, we refute the hypothesis that Ca occupancy of the polycystin-2 intracellular EF hand is responsible for these forms of channel regulation, and, if disrupted, results in ADPKD.

Molecular dysregulation of ciliary polycystin-2 channels caused by variants in the TOP domain.

Genetic variants in which encodes for the polycystin-2 ion channel are responsible for many clinical cases of autosomal dominant polycystic kidney disease (ADPKD). Despite our strong understanding of the genetic basis of ADPKD, we do not know how most variants impact channel function. Polycystin-2 is found in organelle membranes, including the primary cilium-an antennae-like structure on the luminal side of the collecting duct.

Structure and function of polycystin channels in primary cilia.

Variants in genes which encode for polycystin-1 and polycystin-2 cause most forms of autosomal dominant polycystic disease (ADPKD). Despite our strong understanding of the genetic determinants of ADPKD, we do not understand the structural features which govern the function of polycystins at the molecular level, nor do we understand the impact of most disease-causing variants on the conformational state of these proteins. These questions have remained elusive because polycystins localize to several organelle membranes, including the primary cilia.

Opening TRPP2 () requires the transfer of gating charges.

The opening of voltage-gated ion channels is initiated by transfer of gating charges that sense the electric field across the membrane. Although transient receptor potential ion channels (TRP) are members of this family, their opening is not intrinsically linked to membrane potential, and they are generally not considered voltage gated. Here we demonstrate that TRPP2, a member of the polycystin subfamily of TRP channels encoded by the gene, is an exception to this rule.

Metabotropic, but not allosteric, effects of neurosteroids on GABAergic inhibition depend on the phosphorylation of GABA receptors.

Neuroactive steroids (NASs) are synthesized within the brain and exert profound effects on behavior. These effects are primarily believed to arise from the activities of NASs as positive allosteric modulators (PAMs) of the GABA-type A receptor (GABAR). NASs also activate a family of G protein-coupled receptors known as membrane progesterone receptors (mPRs).

Neuroactive Steroids Reverse Tonic Inhibitory Deficits in Fragile X Syndrome Mouse Model.

Fragile X syndrome (FXS) is the most common form of inherited intellectual disability. A reduction in neuronal inhibition mediated by γ-aminobutyric acid type A receptors (GABARs) has been implicated in the pathophysiology of FXS. Neuroactive steroids (NASs) are known allosteric modulators of GABAR channel function, but recent studies from our laboratory have revealed that NASs also exert persistent metabotropic effects on the efficacy of tonic inhibition by increasing the protein kinase C (PKC)-mediated phosphorylation of the α4 and β3 subunits which increase the membrane expression and boosts tonic inhibition.

Deficits in the activity of presynaptic γ-aminobutyric acid type B receptors contribute to altered neuronal excitability in fragile X syndrome.

The behavioral and anatomical deficits seen in fragile X syndrome (FXS) are widely believed to result from imbalances in the relative strengths of excitatory and inhibitory neurotransmission. Although modified neuronal excitability is thought to be of significance, the contribution that alterations in GABAergic inhibition play in the pathophysiology of FXS are ill defined. Slow sustained neuronal inhibition is mediated by γ-aminobutyric acid type B (GABA) receptors, which are heterodimeric G-protein-coupled receptors constructed from R1a and R2 or R1b and R2 subunits.

Regulating the Efficacy of Inhibition Through Trafficking of γ-Aminobutyric Acid Type A Receptors.

Trafficking of anesthetic-sensitive receptors within the plasma membrane, or from one cellular component to another, occurs continuously. Changes in receptor trafficking have implications in altering anesthetic sensitivity. γ-Aminobutyric acid type A receptors (GABAARs) are anion-permeable ion channels and are the major class of receptor in the adult mammalian central nervous system that mediates inhibition.

Compromising the phosphodependent regulation of the GABAAR β3 subunit reproduces the core phenotypes of autism spectrum disorders.

Alterations in the efficacy of neuronal inhibition mediated by GABAA receptors (GABAARs) containing β3 subunits are continually implicated in autism spectrum disorders (ASDs). In vitro, the plasma membrane stability of GABAARs is potentiated via phosphorylation of serine residues 408 and 409 (S408/9) in the β3 subunit, an effect that is mimicked by their mutation to alanines. To assess if modifications in β3 subunit expression contribute to ASDs, we have created a mouse in which S408/9 have been mutated to alanines (S408/9A).

Neurosteroids promote phosphorylation and membrane insertion of extrasynaptic GABAA receptors.

Neurosteroids are synthesized within the brain and act as endogenous anxiolytic, anticonvulsant, hypnotic, and sedative agents, actions that are principally mediated via their ability to potentiate phasic and tonic inhibitory neurotransmission mediated by γ-aminobutyric acid type A receptors (GABAARs). Although neurosteroids are accepted allosteric modulators of GABAARs, here we reveal they exert sustained effects on GABAergic inhibition by selectively enhancing the trafficking of GABAARs that mediate tonic inhibition. We demonstrate that neurosteroids potentiate the protein kinase C-dependent phosphorylation of S443 within α4 subunits, a component of GABAAR subtypes that mediate tonic inhibition in many brain regions.

Direct recording and molecular identification of the calcium channel of primary cilia.

A primary cilium is a solitary, slender, non-motile protuberance of structured microtubules (9+0) enclosed by plasma membrane. Housing components of the cell division apparatus between cell divisions, primary cilia also serve as specialized compartments for calcium signalling and hedgehog signalling pathways. Specialized sensory cilia such as retinal photoreceptors and olfactory cilia use diverse ion channels.

Effects of neonatal stress and morphine on kappa opioid receptor signaling.

Background: Critically ill neonates experience multiple stressors during hospitalization. Opioids are commonly prescribed to ameliorate their pain and stress. However, the enduring effects of stress and opioids are not understood.