We report the first example of a K+ channel beta-subunit that is also a serine/threonine kinase. MPS-1 is a single-transmembrane domain protein that coassembles with voltage-gated K+ channel KVS-1 in the nervous system of the nematode Caenorhabditis elegans. Biochemical analysis shows that MPS-1 can phosphorylate KVS-1 and other substrates. Electrophysiological analysis in Chinese hamster ovary (CHO) cells demonstrates that MPS-1 activity leads to a significant decrease in the macroscopic current. Single-channel analysis and biotinylation assays indicate that MPS-1 reduces the macroscopic current by lowering the open probability of the channel. These data are consistent with a model that predicts that the MPS-1-dependent phosphorylation of KVS-1 sustains cell excitability by controlling K+ flux.

We have identified a family of ancillary subunits of K ؉ channels in Caenorhabditis elegans. MPS-1 and its related members MPS-2, MPS-3, and MPS-4 are detected in the nervous system of the nematode. Electrophysiological analysis in ASE neurons and mammalian cells and epigenetic inactivation by double-stranded RNA interference (RNAi) in vivo show that each MPS can associate with and functionally endow the voltage-gated K ؉ channel KVS-1. In the chemosensory neuron ADF, three different MPS subunits combine with KVS-1 to form both binary (MPS-1⅐KVS-1) and ternary (MPS-2⅐MPS-3⅐KVS-1) complexes. RNAi of mps-2, mps-3, or both, enhance the taste of the animal for sodium without altering the susceptibility to other attractants. When sodium is introduced in the test plate as background or as antagonist attractant, the nematode loses the ability to recognize a second attractant. Thus, it appears that the chemosensory apparatus of C. elegans uses sensory thresholds and that a voltage-gated K ؉ channel is specifically required for this mechanism.Chemosensory function plays a crucial role in the life of the nematode Caenorhabditis elegans. The animal lives in the soil, feeds on bacteria, and adapts to the environment based on chemical cues (1). C. elegans can detect several classes of attractants including salts, amino acids, cyclic nucleotides, and vitamins (2). Chemotaxis to water-soluble attractants is mediated by a group of five bilateral amphid neurons, ASE, ADF, ASG, ASI, and ASK, which are located in the head of the animal (3). Individual amphid neurons can detect multiple cues that are distinguished by the animal (2). It is not clear, however, how the sensory neuron integrates signals corresponding to different attractants to produce a specific output signal and what the role of K ϩ currents is in this process. In a previous paper (4) we reported the identification of a voltage-gated Atype K ϩ channel, KVS-1, that is expressed and operates in C. elegans chemosensory neurons. We further found that KVS-1 can be functionally differentiated by assembly with a beta subunit, a KCNE-related peptide termed MPS-1. Amphid neurons have been reported to exhibit a large variety of A-type K ϩ currents (5). Hence, we speculated that single-transmembrane subunits such as MPS-1 might represent a way to generate functional diversity, and we hypothesized that, by analogy with other species (6, 7), MPS-1-related proteins might exist and operate in C. elegans. This effort led us to discover three novel mps members that establish, together with MPS-1, the C. elegans family of KCNE ancillary subunits of K ϩ channels. MPS-2, -3, and -4 are shown to associate with and to modulate the A-type K ϩ current mediated by KVS-1 in vitro and in vivo. Moreover we show that one of these complexes, resulting from the assembly of MPS-2 and MPS-3 with KVS-1, is specifically involved in tuning the responsiveness of the animal for sodium. MATERIALS AND METHODS Cloning of MPS-2.a, MPS-2.b, MPS-3, and MPS-4 -Cloning was performed with a Smart Race kit (Clonte...

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Conclusions: Measurements of urinary albumin, total protein, and albumin-to-creatinine ratio are minimally affected by storage at ؊70°C for approximately 2.5 yr. Prolonged storage results in small decreases of urinary albumin and protein that do not substantially affect phenotype classification of overt renal disease.

Fatigue is a phenomenon in which force reduction has been linked to impairment of several biochemical processes. In skeletal muscle, the ATP-sensitive potassium channels (K) are actively involved in myoprotection against metabolic stress. They are present in sarcolemma and mitochondria (mitoK channels). K channel openers like nicorandil has been recognized for their ability to protect skeletal muscle from ischemia-reperfusion injury, however, the effects of nicorandil on fatigue in slow skeletal muscle fibers has not been explored, being the aim of this study. Nicorandil (10 μM), improved the muscle function reversing fatigue as increased post-fatigue tension in the peak and total tension significantly with respect to the fatigued condition. However, this beneficial effect was prevented by the mitoK channel blocker 5-hydroxydecanoate (5-HD, 500 μM) and by the free radical scavenger N-2-mercaptopropionyl glycine (MPG, 1 mM), but not by the nitric oxide (NO) synthase inhibitor Nω-nitro-L-arginine methyl ester (L-NAME, 100 μM). Nicorandil also decreased lipid peroxidation and maintained both reduced glutathione (GSH) levels and an elevated GSH/GSSG ratio, whereas total glutathione (TGSH) remained unaltered during post-fatigue tension. In addition, NO production, measured through nitrite concentrations was significantly increased with nicorandil during post-fatigue tension; this increase remained unaltered in the presence of nicorandil plus L-NAME, nonetheless, this effect was reversed with nicorandil plus MPG. Hence, these results suggest that nicorandil improves the muscle function reversing fatigue in slow skeletal muscle fibers of chicken through its effects not only as a mitoK channel opener but also as NO donor and as an antioxidant.