Interactions between beta 2-syntrophin and a family of microtubule-associated serine/threonine kinases.

A screen for proteins that interact with beta 2-syntrophin led to the isolation of MAST205 (microtubule-associated serine/threonine kinase-205 kD) and a newly identified homologue, SAST (syntrophin-associated serine/threonine kinase). Binding studies showed that beta 2-syntrophin and MAST205/SAST associated via a PDZ-PDZ domain interaction. MAST205 colocalized with beta 2-syntrophin and utrophin at neuromuscular junctions. SAST colocalized with syntrophin in cerebral vasculature, spermatic acrosomes and neuronal processes. SAST and syntrophin were highly associated with purified microtubules and microtubule-associated proteins, whereas utrophin and dystrophin were only partially associated with microtubules. Our data suggest that MAST205 and SAST link the dystrophin/utrophin network with microtubule filaments via the syntrophins.

Does bariatric surgery improve adipose tissue function?

Bariatric surgery is currently the most effective treatment for obesity. Not only do these types of surgeries produce significant weight loss but also they improve insulin sensitivity and whole body metabolic function. The aim of this review is to explore how altered physiology of adipose tissue may contribute to the potent metabolic effects of some of these procedures. This includes specific effects on various fat depots, the function of individual adipocytes and the interaction between adipose tissue and other key metabolic tissues. Besides a dramatic loss of fat mass, bariatric surgery shifts the distribution of fat from visceral to the subcutaneous compartment favoring metabolic improvement. The sensitivity towards lipolysis controlled by insulin and catecholamines is improved, adipokine secretion is altered and local adipose inflammation as well as systemic inflammatory markers decreases. Some of these changes have been shown to be weight loss independent, and novel hypothesis for these effects includes include changes in bile acid metabolism, gut microbiota and central regulation of metabolism. In conclusion bariatric surgery is capable of improving aspects of adipose tissue function and do so in some cases in ways that are not entirely explained by the potent effect of surgery. © 2016 World Obesity.

Localization of Dlg at the mammalian neuromuscular junction.

Recent studies have begun to elucidate the localization of ion channels and receptors in central nervous system synapses. A family of proteins containing PDZ domains has been suggested to play essential roles in these processes. PSD-95 and chapsyn-110 have been implicated in the clustering of Shaker K+ channels and NMDA receptors in the mammalian brain, and Dlg plays a role in the clustering of Shaker K+ channels at the Drosophila neuromuscular junction (NMJ). We have explored whether Dlg might participate in mammalian NMJ organization. We demonstrate that Dlg is expressed in muscle and co-localizes with utrophin at the post-synaptic face of the mammalian NMJ. Dlg may therefore be important for establishing or maintaining the organization of protein complexes at the mammalian NMJ.

Expression of the 71 kDa dystrophin isoform (Dp71) evaluated by gene targeting.

To investigate the function of the major non-muscle dystrophin isoform, Dp71, we substituted a beta-galactosidase (betagal) reporter gene for Dp71 by homologous recombination in embryonic stem cells. Staining for betagal activity in chimeric mice revealed Dp71 promoter activity in glial cells in the CNS, in neurons of the inner nuclear and inner plexiform layers of the retina, and in the kidney tubules and collecting ducts. Our observations demonstrate that Dp71 is widely expressed in the adult CNS (retina, cerebellum, cerebral cortex, ependyma, and choroid) as well as the adult kidney epithelium and suggest a broad function for Dp71 in differentiated tissues.

Measurement of hemoglobin-acetaldehyde adduct in alcoholic patients.

A sensitive and specific test for chronic alcohol abuse is useful in the diagnosis and management of alcoholic patients. Herein, we report the measurement of hemoglobin-acetaldehyde adducts (Hb-AA) in alcoholic patients by a sandwich ELISA using different antibodies. Keyhole limpet hemocyanin (KLH), a peptide consists of eight amino acid residues (8-pep, V1 to K8) at the N-terminus of beta-chain of human sickle-cell Hb and a segment of HbA beta-chain consists of 11 amino acids rich in lysine or K (11-pep, G56-K66) were incubated with acetaldehyde and NaCNBH3 to form protein-AAs. 8-Pep-AA and 11-pep-AA were individually conjugated to unmodified KLH as the carrier. Anti-protein-AA IgGs were raised in rabbits using these three protein-AA immunogens. When anti-KLH-AA IgG was used in ELISA, optical densities for alcoholic patients and controls were 0.311 +/- 0.124 and 0.147 +/- 0.042 (means +/- SD, n = 40/group, p < 0.001), respectively. Using mean value +/- 2 SD of controls as the cut-off, sensitivities to detect alcoholic patients were 78, 75, and 43%, respectively, when anti-KLH-AA, anti-11-pep-AA, and anti-8-pep-AA were used. Correlation among optical densities obtained from the first two IgGs was excellent (R2 = 0.905). We conclude that: (1) Hb-AA has the potential of being a good marker for alcohol abuse, and (2) the site of Hb that is modified by acetaldehyde in vivo is primarily located in a surface-accessible domain near the center of the beta-chain of HbA where several lysine residues are clustered.

Interactions between dystrophin and the sarcolemma membrane.

Dystrophin serves as a link between the subsarcolemmal cytoskeleton and the extracellular matrix. The NH2 terminus attaches to the cytoskeleton, while the COOH terminus attaches to the dystrophin associated protein (DAP) complex, which can be separated into the dystroglycan, sarcoglycan, and syntrophin subcomplexes. While the function of each DAP is not known, the dystroglycan complex binds laminin in the extracellular matrix, and binds the dystrophin COOH terminus in vitro. The syntrophins also bind the dystrophin COOH terminus in vitro, but no evidence has been reported for an interaction between dystrophin and the sarcoglycans. Human mutations have been found in dystrophin, the sarcoglycans and laminin, all of which lead to various types of muscular dystrophy. We have been studying the dystrophin domains necessary for formation of a functional complex by generating transgenic mdx (dystrophin minus) mice expressing internally truncated dystrophins. These mice provide in vivo models to study the localization of truncated dystrophin isoforms, the association of the truncated proteins with the DAP complex, and the functional capacity of the assembled DAP complexes. Expression of a dystrophin deleted for most of the NH2-terminal domain in mdx mice leads to only a mild dystrophy, indicating that dystrophin can attach to the cytoskeleton by multiple mechanisms. Truncation of the central rod domain leads to normal DAP complex formation and almost fully prevents development of dystrophy. Deletion analysis of the COOH-terminal regions indicates that a broad cysteine-rich domain is indispensable for dystrophin function. This region coincides with the in vitro identified beta-dystroglycan binding domain. Mice lacking this latter domain express very low levels of the sarcoglycans, indicating that the sarcoglycan complex binds dystrophin via dystroglycan. All deletion constructs tested lead to normal expression of the syntrophins, indicating that syntrophin associates with the DAP complex via multiple binding partners.

Characterization of dystrophin and utrophin diversity in the mouse.

Utrophin is a 400 kDa autosomal homolog of dystrophin and a component of the submembranous cytoskeleton. While multiple dystrophin isoforms have been identified along with alternatively spliced products, to date only two different mRNA species of utrophin have been identified. To determine the degree of evolutionary conservation between dystrophin and utrophin isoforms, we have compared their expression patterns in adult mice. Northern blot analysis of multiple adult tissues confirmed that only two major sizes of transcripts are produced from each gene: 13 and 5.5 kb from utrophin and 14 and 4.8 kb from dystrophin. However, western blot analysis detected several putative short utrophin isoforms that may be homologs of the dystrophin isoforms Dp140, Dp116 and Dp71. We also identified an alternatively spliced utrophin transcript that lacks the equivalent of the alternatively spliced dystrophin exon 71. Finally, we demonstrated that the C-terminal domain of utrophin targeted to neuromuscular junctions in normal mice, but localized to the sarcolemma efficiently only in the absence of dystrophin. Our results provide further evidence for a common evolutionary origin of the utrophin and dystrophin genes.