Genetic Deletion of KLHL1 Leads to Hyperexcitability in Hypothalamic POMC Neurons and Lack of Electrical Responses to Leptin.

Kelch-like 1 (KLHL1) is a neuronal actin-binding protein that modulates voltage-gated calcium channels. The KLHL1 knockout (KO) model displays altered calcium channel expression in various brain regions. We analyzed the electrical behavior of hypothalamic POMC (proopiomelanocortin) neurons and their response to leptin.

TRPC1/5-Ca 3 Complex Mediates Leptin-Induced Excitability in Hypothalamic Neurons.

Leptin regulates hypothalamic POMC (pro-opiomelanocortin) neurons by inducing TRPC (Transient Receptor Potential Cation) channel-mediate membrane depolarization. The role of TRPC channels in POMC neuron excitability is clearly established; however, it remains unknown whether their activity alone is sufficient to trigger excitability. Here we show that the right-shift voltage induced by the leptin-induced TRPC channel-mediated depolarization of the resting membrane potential brings T-type channels into the active window current range, resulting in an increase of the steady state T-type calcium current from 40 to 70% resulting in increased intrinsic excitability of POMC neurons.

Calcium current homeostasis and synaptic deficits in hippocampal neurons from Kelch-like 1 knockout mice.

Kelch-like 1 (KLHL1) is a neuronal actin-binding protein that modulates voltage-gated CaV2.1 (P/Q-type) and CaV3.2 (α1H T-type) calcium channels; KLHL1 knockdown experiments (KD) cause down-regulation of both channel types and altered synaptic properties in cultured rat hippocampal neurons (Perissinotti et al.

Down-regulation of endogenous KLHL1 decreases voltage-gated calcium current density.

The actin-binding protein Kelch-like 1 (KLHL1) can modulate voltage-gated calcium channels in vitro. KLHL1 interacts with actin and with the pore-forming subunits of Cav2.1 and CaV3.

Elimination of the actin-binding domain in kelch-like 1 protein induces T-type calcium channel modulation only in the presence of action potential waveforms.

The Kelch-like 1 protein (KLHL1) is a neuronal actin-binding protein that modulates calcium channel function. It increases the current density of Ca(v)3.2 (α(1H)) calcium channels via direct interaction with α(1H) and actin-F, resulting in biophysical changes in Ca(v)3.

Insulin-mediated upregulation of T-type Ca2+ currents in GH3 cells is mediated by increased endosomal recycling and incorporation of surface membrane Cav3.1 channels.

Growth factors and hormones have both short- and long-term regulatory effects on the functional expression of voltage gated Ca2+ (CaV) channels. In particular, it has been reported that chronic treatment with insulin upregulates T-type channel membrane expression, leading to an increase in current density in clonal pituitary GH3 cells. Though this regulatory action may result from alterations in gene expression, recent studies have demonstrated also that endosomal trafficking provides a mechanism for dynamic changes in CaV channel membrane density.

Forced-exercise delays neuropathic pain in experimental diabetes: effects on voltage-activated calcium channels.

Physical exercise produces a variety of psychophysical effects, including altered pain perception. Elevated levels of centrally produced endorphins or endocannabinoids are implicated as mediators of exercise-induced analgesia. The effect of exercise on the development and persistence of disease-associated acute/chronic pain remains unclear.

Kelch-like 1 protein upregulates T-type currents by an actin-F dependent increase in α(1H) channels via the recycling endosome.

The neuronal protein Kelch-like 1 (KLHL1) is a novel actin-binding protein that modulates neuronal structure and function. KLHL1 knockout mice exhibit dendritic atrophy in cerebellar Purkinje neurons and motor dysfunction. Interestingly, KLHL1 upregulates high and low voltage-gated calcium currents (Ca(V)2.

Altered frequency-dependent inactivation and steady-state inactivation of polyglutamine-expanded alpha1A in SCA6.

Spinocerebellar ataxia type 6 (SCA6) is a neurodegenerative disease of the cerebellum and inferior olives characterized by a late-onset cerebellar ataxia and selective loss of Purkinje neurons. SCA6 arises from an expansion of the polyglutamine tract located in exon 47 of the alpha(1A) (P/Q-type calcium channel) gene from a nonpathogenic size of 4 to 18 glutamines (CAG(4-18)) to CAG(19-33) in SCA6. The molecular basis of SCA6 is poorly understood.

Presynaptic Ca2+ channels compete for channel type-preferring slots in altered neurotransmission arising from Ca2+ channelopathy.

Several human channelopathies result from mutations in alpha1A, the pore-forming subunit of P/Q-type Ca2+ channels, conduits of presynaptic Ca2+ entry for evoked neurotransmission. We found that wild-type human alpha1A subunits supported transmission between cultured mouse hippocampal neurons equally well as endogenous mouse alpha1A, whereas introduction of impermeant human alpha1A hampered the effect of endogenous subunits. Thus, presynaptic P/Q-type channels may compete for channel type-preferring "slots" that limit their synaptic effectiveness.

Presynaptic homeostasis at CNS nerve terminals compensates for lack of a key Ca2+ entry pathway.

At central synapses, P/Q-type Ca(2+) channels normally provide a critical Ca(2+) entry pathway for neurotransmission. Nevertheless, we found that nerve terminals lacking alpha(1A) (Ca(V)2.1), the pore-forming subunit of P/Q-type channels, displayed a remarkable preservation of synaptic function.

Ca2+ channels and synaptic transmission at the adult, neonatal, and P/Q-type deficient neuromuscular junction.

Different types of voltage-activated Ca(2+) channels have been established based on their molecular structure and pharmacological and biophysical properties. One of them, the P/Q-type, is the main channel involved in nerve-evoked neurotransmitter release at neuromuscular junctions and the immunological target in Eaton-Lambert Syndrome. At adult neuromuscular junctions, L- and N-type Ca(2+) channels become involved in transmitter release only under certain experimental or pathological conditions.

Altered properties of quantal neurotransmitter release at endplates of mice lacking P/Q-type Ca2+ channels.

Transmission at the mouse neuromuscular junction normally relies on P/Q-type channels, but became jointly dependent on both N- and R-type Ca(2+) channels when the PQ-type channel alpha(1A) subunit was deleted. R-type channels lay close to Ca(2+) sensors for exocytosis and I(K(Ca)) channel activation, like the P/Q-type channels they replaced. In contrast, N-type channels were less well localized, but abundant enough to influence secretion strongly, particularly when action potentials were prolonged.

alpha- and betaCaMKII. Inverse regulation by neuronal activity and opposing effects on synaptic strength.

We show that alpha and betaCaMKII are inversely regulated by activity in hippocampal neurons in culture: the alpha/beta ratio shifts toward alpha during increased activity and beta during decreased activity. The swing in ratio is approximately 5-fold and may help tune the CaMKII holoenzyme to changing intensities of Ca(2+) signaling. The regulation of CaMKII levels uses distinguishable pathways, one responsive to NMDA receptor blockade that controls alphaCaMKII alone, the other responsive to AMPA receptor blockade and involving betaCaMKII and possibly further downstream effects of betaCaMKII on alphaCaMKII.