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Proteostasis maintenance of γ-aminobutyric acid type A (GABAA) receptors dictates their function in controlling neuronal inhibition in mammalian central nervous systems. However, as a multisubunit, multispan, integral membrane protein, even wild type subunits of GABAA receptors fold and assemble inefficiently in the endoplasmic reticulum (ER). Unassembled and misfolded subunits undergo ER-associated degradation (ERAD), but this degradation process remains poorly understood forGABAA receptors. Here, using the α1 subunits of GABAA receptors as a model substrate, we demonstrated that Grp94, a metazoan-specific Hsp90 in the ER lumen, uses its middle domain to interact with theα1 subunits and positively regulates their ERAD. OS-9, an ER-resident lectin, acts downstream of Grp94 to further recognize misfolded α1 subunits in a glycan-dependent manner. This delivers misfoldedα1 subunits to the Hrd1-mediated ubiquitination and the valosin-containing protein-mediated extraction pathway. Repressing the initial ERAD recognition step by inhibiting Grp94 enhances the functional surface expression of misfolding-proneα1(A322D) subunits, which causes autosomal dominant juvenile myoclonic epilepsy. This study clarifies a Grp94-mediated ERAD pathway for GABAA receptors, which provides a novel way to finely tune their function in physiological and pathophysiological conditions. [ABSTRACT FROM AUTHOR]

Coenzyme A (CoA) mediates thiol-based acyl-group transfer (acetylation and palmitoylation). However, a role for CoA in the thiol-based transfer of NO groups (S-nitrosylation) has not been considered. Here we describe protein S-nitrosylation in yeast (heretofore unknown) that is mediated by S-nitroso-CoA (SNO-CoA). We identify a specific SNO-CoA reductase encoded by the alcohol dehydrogenase 6 (ADH6) gene and show that deletion of ADH6 increases cellular S-nitrosylation and alters CoA metabolism. Further, we report that Adh6, acting as a selective SNO-CoA reductase, protects acetoacetyl-CoA thiolase from inhibitory S-nitrosylation and thereby affects sterol biosynthesis. Thus, Adh6-regulated, SNO-CoA-mediated protein S-nitrosylation provides a regulatory mechanism paralleling protein acetylation. We also find that SNO-CoA reductases are present from bacteria to mammals, and we identify aldo-keto reductase 1A1 as the mammalian functional analog of Adh6. Our studies reveal a novel functional class of enzymes that regulate protein S-nitrosylation from yeast to mammals and suggest that SNO-CoA-mediated S-nitrosylation may subserve metabolic regulation. [ABSTRACT FROM AUTHOR]

The thermal stability of sheepskin collagen cross-linked with chrome sulfate and mimosa (MI)–oxazolidine (OZ), respectively, had been researched in this experiment. All samples’ shrinkage temperatures ( Ts) are determined by a special Ts-testing-apparatus and denaturation temperatures ( Td) are determined by the differential scanning calorimetry. The relations between the modified collagens containing moisture and their hydrothermal stability, Ts or Td, were studied. The results show that the cross linking agents can enhance the thermal stability of modified collagen whose Ts are 109.8 and 110.6 °C for collagen treated with chrome and MI–OZ, respectively. When the samples contain 25–71.9% moisture for chrome leather and 20–71.1% for leather treated with MI–OZ, the hydrothermal stability will decrease with the increase of moisture. It was found that the difference between Ts and Td of collagen modified by chrome is more obvious than that of collagen modified with MI–OZ. And when the moisture of chrome leather exceeds 55%, Td cannot express thermal stability of modified collagen as a substitute for Ts, and the moisture is 40% for leather tanned with MI–OZ. [ABSTRACT FROM AUTHOR]

The thermal decomposition process of the complex [Cu(NBOCTB)][Cu(NO3)4] H2O has been studied by TG and DTG technique, and possible intermediates of the thermal decomposition have also been conjectured from the TG and DTG curves. The results suggest that the decomposition of the complex involves five steps: The non-isothermal kinetics of steps 1, 2 and 3 have been studied by means of the Achar and Coats-Redfern method based on TG and DTG curves. Step 1 is a ‘Coring and Growth’ mechanism ( n= 1), its kinetic equation may be expressed as: dα/d t=Ae−E/RT(1−α). Steps 2 and 3 are both ‘two order chemical reaction’ mechanisms, their kinetic equations can be expressed as: dα/d t=Ae−E/RT(1−α)2. [ABSTRACT FROM AUTHOR]

The ryanodine receptor/Ca2+-release channels (RyRs) of skeletal and cardiac muscle are essential for Ca2+ release from the sarcoplasmic reticulum that mediates excitation-contraction coupling. It has been shown that RyR activity is regulated by dynamic post-translational modifications of Cys residues, in particular S-nitrosylation and S-oxidation. Here we show that the predominant form of RyR in skeletal muscle, RyR1, is subject to Cys-directed modification by S-palmitoylation. S-Palmitoylation targets 18 Cys within the N-terminal, cytoplasmic region of RyR1, which are clustered in multiple functional domains including those implicated in the activity-governing protein-protein interactions of RyR1 with the L-type Ca2+ channel Cav1.1, calmodulin, and the FK506-binding protein FKBP12, as well as in "hot spot" regions containing sites of mutations implicated in malignant hyperthermia and central core disease. Eight of these Cys have been identified previously as subject to physiological S-nitrosylation or S-oxidation. Diminishing S-palmitoylation directly suppresses RyR1 activity as well as stimulus-coupled Ca2+ release through RyR1. These findings demonstrate functional regulation of RyR1 by a previously unreported post-translational modification and indicate the potential for extensive Cys-based signaling cross-talk. In addition, we identify the sarco/endoplasmic reticular Ca2+-ATPase 1A and the α1S subunit of the L-type Ca2+ channel Cav1.1 as S-palmitoylated proteins, indicating that S-palmitoylation may regulate all principal governors of Ca2+ flux in skeletal muscle that mediates excitation-contraction coupling. [ABSTRACT FROM AUTHOR]

Endogenous S-nitrosylation of proteins, a principal mechanism of cellular signaling in eukaryotes, has not been observed in microbes. We report that protein S-nitrosylation is an obligate concomitant of anaerobic respiration on nitrate in Escherichia coli. Endogenous S-nitrosylation during anaerobic respiration is controlled by the transcription factor OxyR, previously thought to operate only under aerobic conditions. Deletion of OxyR resulted in large increases in protein S-nitrosylation, and S-nitrosyiation of OxyR induced transcription from a regulon that is distinct from the regulon induced by OxyR oxidation. Furthermore, products unique to the anaerobic regulon protected against S-nitrosothiols, and anaerobic growth of E. coli lacking OxyR was impaired on nitrate. Thus, OxyR serves as a master regulator of S-nitrosylation, and alternative posttranslational modifications of OxyR control distinct transcriptional responses. [ABSTRACT FROM AUTHOR]