Chapmanabildtrup9348

Overexpression of γ-glutamyl transpeptidase(GGT1) has been implicated in an array of humandiseases including asthma, reperfusion injury,and cancer. Inhibitors are needed for therapy, butdevelopment of potent, specific inhibitors ofGGT1 has been hampered by a lack of structuralinformation regarding substrate binding andcleavage. To enhance our understanding of themolecular mechanism of substrate cleavage, wehave solved the crystal structures of humanGGT1 (hGGT1) with glutathione (a substrate)and a phosphate-glutathione analog (anirreversible inhibitor) bound in the active site.These are the first structures of any eukaryoticGGT with the cysteinylglycine region of thesubstrate-binding site occupied. These structuresand the structure of apo-hGGT reveal movementof amino acid residues within the active site as thesubstrate binds. Asn-401 and Thr-381 each formhydrogen bonds with two atoms of GSH spanningthe γ-glutamyl bond. Three different atoms ofhGGT1 interact with the carboxyl-oxygen of thecysteine of GSH. Interactions between theenzyme and substrate change as the substratemoves deeper into the active site cleft. Thesubstrate reorients and a new hydrogen bond isformed between the substrate and the oxyanionhole. Thr-381 is locked into a singleconformation as an acyl bond forms between thesubstrate and the enzyme. These data provideinsight on a molecular level into the substratespecificity of hGGT1 and provide an explanationfor seemingly disparate observations regardingthe enzymatic activity of hGGT1 mutants. Thisknowledge will aid in the design of clinicallyuseful hGGT1 inhibitors.The ClC-2 chloride channel is expressed in the plasma membrane of almost all mammalian cells. Mutations that cause the loss of ClC-2 function lead to retinal and testicular degeneration and leukodystrophy, whereas gain of function mutations cause hyper-aldosteronism. Leukodystrophy is also observed with a loss of GlialCAM, a cell adhesion molecule which binds to ClC-2 in glia. GlialCAM changes the localization of ClC-2 and opens the channel by altering its gating. We now used cell-type specific deletion of ClC-2 in mice to show that retinal and testicular degeneration depend on a loss of ClC-2 in retinal pigment epithelial cells and Sertoli cells, respectively, whereas leukodystrophy was fully developed only when ClC-2 was disrupted in both astrocytes and oligodendrocytes. The leukodystrophy of Glialcam-/- mice could not be rescued by crosses with Clcn2op/op mice in which a mutation mimics the 'opening' of ClC-2 by GlialCAM. These data indicate that GlialCAM-induced changes in biophysical properties of ClC-2 are irrelevant for GLIALCAM-related leukodystrophy. Taken together, our findings suggest that the pathology caused by Clcn2 disruption results from disturbed extracellular ion homeostasis and identifies the cells involved in this process.Tubby-like proteins (TULPs) are characterized by a conserved C-terminal domain that binds phosphoinositides. Collectively, mammalian TULP1-4 proteins play essential roles in intracellular transport, cell differentiation, signaling, and motility. Yet, little is known about how the function of these proteins is regulated in cells. Here, we present the protein-protein interaction network of TULP3, a protein that is responsible for the trafficking of G-protein coupled receptors to cilia, and whose aberrant expression is associated with severe developmental disorders and polycystic kidney disease. We identify several protein interaction nodes linked to TULP3 that include enzymes involved in acetylation and ubiquitination. We show that acetylation of two key lysine residues on TULP3 by p300 increases TULP3 protein abundance, and that deacetylation of these sites by HDAC1 decreases protein levels. Furthermore, we show that one of these sites is ubiquitinated in the absence of acetylation, and that acetylation inversely correlates with ubiquitination of TULP3. This mechanism is evidently conserved across species and is active in zebrafish during development. this website Finally, we identify this same regulatory module in TULP1, TULP2, and TULP4, and demonstrate that the stability of these proteins is similarly modulated by an acetylation switch. This study unveils a signaling pathway that links nuclear enzymes to ciliary membrane receptors via TULP3, describes a dynamic mechanism for the regulation of all tubby-like proteins, and explores how to exploit it pharmacologically using drugs.All that we view of the world begins with an ultrafast cis to trans photoisomerization of the retinylidene chromophore associated with the visual pigments of rod and cone photoreceptors. The continual responsiveness of these photoreceptors is then sustained by regeneration processes that convert the trans- retinoid back to an 11-cis configuration. Recent biochemical and electrophysiological analyses of the retinal G protein-coupled receptor (RGR) suggest that it could sustain the responsiveness of photoreceptor cells, particularly cones, even under bright light conditions. Thus, two mechanisms have evolved to accomplish the re-isomerization one involving the well-studied retinoid isomerase (RPE65), and a second photoisomerase reaction mediated by the RGR. Impairments to the pathways that transform all- trans-retinal back to 11-cis-retinal are associated with mild to severe forms of retinal dystrophy. Moreover, with age there also is a decline in the rate of chromophore regeneration. Both pharmacological and genetic approaches are being used to bypass visual cycle defects and consequently mitigate blinding diseases. Rapid progress in the use of genome editing also is paving the way for the treatment of disparate retinal diseases. In this review, we provide an update on visual cycle biochemistry and then discuss visual cycle-related diseases and emerging therapeutics for these disorders. There is hope that these advances will be helpful in treating more complex diseases of the eye, including age-related macular degeneration (AMD).Hexokinase (HK) catalyzes the first step in glucose metabolism, making it an exciting target for the inhibition of tumor initiation and progression due to their elevated glucose metabolism. The upregulation of hexokinase-2 (HK2) in many cancers and its limited expression in normal tissues makes it a particularly attractive target for the selective inhibition of cancer growth and the eradication of tumors with limited side effects. The design of such safe and effective anticancer therapeutics requires the development of HK2-specific inhibitors that will not interfere with other HK isozymes. As HK2 is unique among HKs in having a catalytically active N-terminal domain (NTD), we have focused our attention on this region. We previously found that NTD activity is affected by the size of the linker helix-α13 that connects the N- and C-terminal domains of HK2. Three non-active site residues (D447, S449, and K451) at the beginning of the linker helix-α13 have been found to regulate the NTD activity of HK2. Mutation of these residues led to increased dynamics, as shown via hydrogen-deuterium exchange analysis and molecular dynamic simulations.