Cobblestone (type II) lissencephaly and mental retardation are characteristic features of a subset of congenital muscular dystrophies that include Walker-Warburg syndrome, muscle-eye-brain disease, and Fukuyama-type congenital muscular dystrophy. Although the majority of clinical cases are genetically undefined, several causative genes have been identified that encode known or putative glycosyltransferases in the biosynthetic pathway of dystroglycan. Here we test the effects of brain-specific deletion of dystroglycan, and show distinct functions for neuronal and glial dystroglycan. Deletion of dystroglycan in the whole brain produced glial/neuronal heterotopia resembling the cerebral cortex malformation in cobblestone lissencephaly. In wild-type mice, dystroglycan stabilizes the basement membrane of the glia limitans, thereby supporting the cortical infrastructure necessary for neuronal migration. This function depends on extracellular dystroglycan interactions, since the cerebral cortex developed normally in transgenic mice that lack the dystroglycan intracellular domain. Also, forebrain histogenesis was preserved in mice with neuron-specific deletion of dystroglycan, but hippocampal long-term potentiation was blunted, as is also the case in the Large myd mouse, in which dystroglycan glycosylation is disrupted. Our findings provide genetic evidence that neuronal dystroglycan plays a role in synaptic plasticity and that glial dystroglycan is involved in forebrain development. Differences in dystroglycan glycosylation in distinct cell types of the CNS may contribute to the diversity of dystroglycan function in the CNS, as well as to the broad clinical spectrum of type II lissencephalies.

Large-conductance Ca2+- and voltage-activated K+ (BKCa, MaxiK or Slo1) channels are expressed in almost every tissue in our body and participate in many critical functions such as neuronal excitability, vascular tone regulation and neurotransmitter release. The functional versatility of BKCa channels owes in part to the availability of a spectacularly wide array of biological modulators of the channel function. In this review, we focus on modulation of BKCa channels by small endogenous molecules, emphasizing their molecular mechanisms. The mechanistic information available from studies on the small naturally occurring modulators is expected to contribute to our understanding of the physiological and pathophysiological roles of BKCa channels.

Long-chain polyunsaturated omega-3 fatty acids such as docosahexaenoic acid (DHA), found abundantly in oily fish, may have diverse health-promoting effects, potentially protecting the immune, nervous, and cardiovascular systems. However, the mechanisms underlying the purported health-promoting effects of DHA remain largely unclear, in part because molecular signaling pathways and effectors of DHA are only beginning to be revealed. In vascular smooth muscle cells, large-conductance Ca 2+ -and voltage-activated K + (BK) channels provide a critical vasodilatory influence. We report here that DHA with an EC 50 of ∼500 nM rapidly and reversibly activates BK channels composed of the pore-forming Slo1 subunit and the auxiliary subunit β1, increasing currents by up to ∼20-fold. The DHA action is observed in cell-free patches and does not require voltage-sensor activation or Ca 2+ binding but involves destabilization of the closed conformation of the ion conduction gate. DHA lowers blood pressure in anesthetized wildtype but not in Slo1 knockout mice. DHA ethyl ester, contained in dietary supplements, fails to activate BK channels and antagonizes the stimulatory effect of DHA. Slo1 BK channels are thus receptors for long-chain omega-3 fatty acids, and these fatty acids-unlike their ethyl ester derivatives-activate the channels and lower blood pressure. This finding has practical implications for the use of omega-3 fatty acids as nutraceuticals for the general public and also for the critically ill receiving omega-3-enriched formulas.fish oil | lipids | K Ca 1.1 | immunonutrition

Carbon monoxide (CO) is a lethal gas, but it is also increasingly recognized as a physiological signaling molecule capable of regulating a variety of proteins. Among them, large-conductance Ca 2؉ -and voltage-gated K ؉ (Slo1 BK) channels, important in vasodilation and neuronal firing, have been suggested to be directly stimulated by CO. However, the molecular mechanism of the stimulatory action of CO on the Slo1 BK channel has not been clearly elucidated. We report here that CO reliably and repeatedly activates Slo1 BK channels in excised membrane patches in the absence of Ca 2؉ in a voltage-sensor-independent manner. The stimulatory action of CO on the Slo1 BK channel requires an aspartic acid and two histidine residues located in the cytoplasmic RCK1 domain, and the effect persists under the conditions known to inhibit the conventional interaction between CO and heme in other proteins. We propose that CO acts as a partial agonist for the high-affinity divalent cation sensor in the RCK1 domain of the Slo1 BK channel.C arbon monoxide (CO) is a deadly poisonous gas. However, CO is physiologically produced during the course of heme catabolism by heme oxygenases (HMOXs) in an oxygendependent manner, and it is increasingly recognized as a biological signaling molecule important in numerous physiological and pathophysiological processes, including synaptic plasticity, regulation of vascular tone, and tumor proliferation (1). To regulate the wide array of cellular functions, CO typically exerts its action by binding to the reduced heme iron center (Fe 2ϩ ) in hemoproteins (2, 3), thereby altering the way the heme prosthetic group is coordinated (4). The heme-dependent action of CO is exemplified by its stimulatory effect on soluble guanylate cyclase, in which binding of CO to the reduced heme iron center increases the catalytic activity, leading to an enhanced production of cGMP (4, 5).Large-conductance Ca 2ϩ -and voltage-activated K ϩ (Slo1 BK or K Ca 1.1) channels, important in many physiological phenomena, including oxygen sensing, vasodilation, and neuronal firing (6, 7), are also stimulated by . The modulation of Slo1 BK channels by CO is physiologically and pathophysiologically important. For example, the stimulatory effect of CO on Slo1 BK channels underlies its well documented vasodilatory effect (9,11,(13)(14)(15), and the use of CO has been suggested as a potential therapeutic strategy against pulmonary hypertension (11). Production of CO by HMOXs requires oxygen (1), and this oxygen dependence raises the possibility that changes in cellular oxygen tension regulate the Slo1 BK channel activity indirectly by regulating the availability of CO (16). HMOX-2, one member of the HMOX family, may colocalize with Slo1 to allow efficient modulation of the channel by CO according to the local oxygen level (16).Gating of the Slo1 BK channel involves allosteric interactions among the main pore gate, voltage sensor domains, and cytoplasmic RCK1 and RCK2 domains with multiple divalent cation sensors (17,18). Although incre...

Background and Purpose-Ischemic injury can induce neurogenesis in the striatum. Those newborn neurons can express glutamic acid decarboxylase and choline acetyltransferase, markers of GABAergic and cholinergic neurons, respectively. The present study investigated whether these GABAergic and cholinergic new neurons could differentiate into functional cells. Methods-Retrovirus containing the EGFP gene was used to label dividing cells in striatal slices prepared from adult rat brains after middle cerebral artery occlusion. EGFP-targeted immunostaining and immunoelectron microscopy were performed to detect whether newborn neurons could anatomically form neuronal polarity and synapses with pre-existent neurons. Patch clamp recording on acute striatal slices of brains at 6 to 8 weeks after middle cerebral artery occlusion was used to determine whether the newborn neurons could display functional electrophysiological properties. Results-EGFP-expressing (EGFPϩ ) signals could be detected mainly in the cell body in the first 2 weeks. From the fourth to thirteenth weeks after their birth, EGFP ϩ neurons gradually formed neuronal polarity and showed a time-dependent increase in dendrite length and branch formation. EGFP ϩ cells were copositive for NeuN and glutamic acid decarboxylase (EGFP ϩ -NeuN ϩ -GAD 67 ϩ ), MAP-2, and choline acetyltransferase (EGFP ϩ -MAP-2 ϩ -ChAT ϩ ). They also expressed phosphorylated synapsin I (EGFP ϩ -p-SYN ϩ ) and showed typical synaptic structures comprising dendrites and spines. Both GABAergic and cholinergic newborn neurons could fire action potentials and received excitatory and inhibitory synaptic inputs because they displayed spontaneous postsynaptic currents in picrotoxin-and CNQX-inhibited manners. Conclusion-Ischemia-induced newly formed striatal GABAergic and cholinergic neurons could become functionally integrated into neural networks in the brain of adult rats after stroke.