Glucose influences endometrial receptivity to embryo implantation through O-GlcNAcylation-mediated regulation of the cytoskeleton

Phenotypic changes to endometrial epithelial cells underpin receptivity to embryo implantation at the onset of pregnancy but the effect of hyperglycaemia on these processes remains poorly understood. Here we show that physiological levels of glucose (5mM) abolished receptivity in the endometrial epithelial cell line, Ishikawa. However, embryo attachment was supported by 17mM glucose as a result of glucose flux through the hexosamine biosynthetic pathway (HBP) and modulation of cell function via protein O-GlcNAcylation. Pharmacological inhibition of HBP or protein O-GlcNAcylation reduced embryo attachment in co-cultures at 17mM glucose. Mass spectrometry analysis of the O-GlcNAcylated proteome in Ishikawa cells revealed that myosin phosphatase target subunit 1 (MYPT1) is more highly O-GlcNAcylated in 17mM glucose, correlating with loss of its target protein, phospho-myosin light chain 2, from apical cell junctions of polarised epithelium. 2D and 3D morphologic analysis demonstrated that the higher glucose level attenuates epithelial polarity through O-GlcNAcylation. Inhibition of RhoA-associated kinase (ROCK) or myosin II led to reduced polarity and enhanced receptivity in cells cultured in 5mM glucose, consistent with data showing that MYPT1 acts downstream of ROCK signalling. These data implicate regulation of endometrial epithelial polarity through RhoA signaling upstream of actomyosin contractility in the acquisition of endometrial receptivity. Glucose levels impinge on this pathway through O-GlcNAcylation of MYPT1, which may impact endometrial receptivity to an implanting embryo in women with diabetes

Tumor Suppressor Protein p53 Recruits Human Sin3B/HDAC1 Complex for Down-Regulation of Its Target Promoters in Response to Genotoxic Stress

Master regulator protein p53, popularly known as the “guardian of genome” is the hub for regulation of diverse cellular pathways. Depending on the cell type and severity of DNA damage, p53 protein mediates cell cycle arrest or apoptosis, besides activating DNA repair, which is apparently achieved by regulation of its target genes, as well as direct interaction with other proteins. p53 is known to repress target genes via multiple mechanisms one of which is via recruitment of chromatin remodelling Sin3/HDAC1/2 complex. Sin3 proteins (Sin3A and Sin3B) regulate gene expression at the chromatin-level by serving as an anchor onto which the core Sin3/HDAC complex is assembled. The Sin3/HDAC co-repressor complex can be recruited by a large number of DNA-binding transcription factors. Sin3A has been closely linked to p53 while Sin3B is considered to be a close associate of E2Fs. The theme of this study was to establish the role of Sin3B in p53-mediated gene repression. We demonstrate a direct protein-protein interaction between human p53 and Sin3B (hSin3B). Amino acids 1–399 of hSin3B protein are involved in its interaction with N-terminal region (amino acids 1–108) of p53. Genotoxic stress induced by Adriamycin treatment increases the levels of hSin3B that is recruited to the promoters of p53-target genes (HSPA8, MAD1 and CRYZ). More importantly recruitment of hSin3B and repression of the three p53-target promoters upon Adriamycin treatment were observed only in p53+/+ cell lines. Additionally an increased tri-methylation of the H3K9 residue at the promoters of HSPA8 and CRYZ was also observed following Adriamycin treatment. The present study highlights for the first time the essential role of Sin3B as an important associate of p53 in mediating the cellular responses to stress and in the transcriptional repression of genes encoding for heat shock proteins or proteins involved in regulation of cell cycle and apoptosis

Autoacetylation of Purified Calreticulin Transacetylase Utilizing Acetoxycoumarin as the Acetyl Group Donor

Our earlier reports documented that calreticulin, a multifunctional Ca(2+)-binding protein in endoplasmic reticulum lumen, possessed protein acetyltransferase function termed Calreticulin Transacetylase (CRTAase). The autoacetylation of purified human placental CRTAase concomitant with the acetylation of receptor proteins by a model acetoxycoumarin, 7,8-Diacetoxy-4-methylcoumarin, was observed. Here, we have examined the autoacetylation property of CRTAase by immunoblotting and mass spectrometry. Ca(2+) was found to inhibit CRTAase activity. The inhibition of both autoacetylation of CRTAase as well as acetylation of the receptor protein was apparent when Ca(2+) was included in the reaction mixture as visualized by interaction with anti-acetyl lysine antibody. The acetylation of lysines residues: -48, -62, -64, -153, and -159 in N-domain and -206, -207, -209, and -238 in P-domain of CRTAase were located by high-performance liquid chromatography-electronspray ionization tandem mass spectrometry. Further, computer assisted protein structure modeling studies were undertaken to probe the effect of autoacetylation of CRTAase. Accordingly, the predicted CRTAase 3D model showed that all the loop regions of both N- and P-domain bear the acetylated lysines. Energy minimization of the acetylated residues revealed charge neutralization of lysines due to the N-epsilon-acetylation which may facilitate the interaction of CRTAase with the protein substrate and the subsequent transacetylase action

Solitary submucous neurofibroma of the mandible: review of the literature and report of a rare case

<p>Abstract</p> <p>Solitary neurofibroma is a rare benign non-odontogenic tumor. Particularly in the oral cavity, neurogenic tumors are rare, especially if they are malignant. Neurofibromas may present either as solitary lesions or as part of the generalised syndrome of neurofibromatosis or von Recklinghausen's disease of the skin. Clinically, oral neurofibromas usually appear as pediculated or sessile nodules, with slow growth and mostly without pain. The diagnosis can be confirmed by histological examination. Neurofibromas are immunopositive for the S-100 protein, indicating its neural origin. Treatment is surgical and the prognosis is excellent. For illustration a rare case of a solitary neurofibroma in the mandible is presented.</p