Isolation of dopamine D-2 receptor (D2R) promoters in Mugil cephalus

This paper reports the isolation of two putative D2R promoters from grey mullet, one 5' flanking and the other an intronic sequence immediately upstream of the first coding exon. Promoter activity of the intronic sequence was confirmed in vitro through functional analysis using luciferase as reporter gene. The functional characteristics of the region flanking the 5'-UTR is currently under investigation.

Binding and internalization of the melanocyte stimulating hormone receptor ligand [Nle(4), D-Phe(7)]alpha-MSH in B16 melanoma cells

The current study aims to ascertain the fate of the melanocyte stimulating hormone (MSH) receptor and its ligand [Nle(4), D-Phe(7)]alpha-MsH (NDP-MSH) following binding to murine B16 melanoma cells. Cells were incubated with [I-125]-NDP-MSH for up to 180 min and binding, internalization and degradation determined. Intracellular trafficking of the radiolabel was assessed !using Percoll density gradient centrifugation of homogenized cells. Receptor down-regulation and receptor mRNA levels were also measured over 96 hr after exposure to 1 mu M ligand. NDP-MSH accumulation increased with time in a temperature-dependent manner and was inhibited by excess peptide. The ligand was rapidly internalized and translocated to the lysosomal compartment where it was degraded. Internalization was accompanied by a loss or down-regulation of cell surface receptors, suggesting internalization of the NDP-MSH-receptor complex. No recycling of the receptors between the plasma membrane and intracellular compartments could be detected in this cell-hue. Approximately 15% of the surface receptors were resistant to down-regulation, possibly indicating receptor heterogeneity. Down-regulation persisted ibr up to 96 hr and was accompanied by a decrease in MSH receptor mRNA levels 48 hr after treatment. However, before this time, transcript levels were the same in treated and control cells. In contrast to what was seen with NDP-MSH, cell surface receptors removed with trypsin wc:re rapidly replaced. These results show that NDP-MSH not only induced MSH receptor :internalization but also inhibited receptor turnover, resulting in a prolonged down-regulation. It is concluded that, in B16 cells, the MSH receptor undergoes ligand-dependent internalization, resulting in a prolonged down-regulation. Copyright (C) 1996 Elsevier Science Ltd

d-cube decompositions of K-n/K-m

Necessary conditions on n, m and d are given for the existence of an edge-disjoint decomposition of K-n\K-m into copies of the graph of a d-dimensional cube. Sufficiency is shown when d = 3 and, in some cases, when d = 2(t). We settle the problem of embedding 3-cube decompositions of K-m into 3-cube decompositions of K-n; where n greater than or equal to m.

Transient expression of a novel serine protease in the ectoderm of the ascidian Herdmania momus during development

We have studied gene expression during ascidian embryonic development using the technique of differential display and isolated partial cDNA sequences of 12 genes. Developmental regulation of these genes has been confirmed by northern hybridization analysis. Further cDNA cloning and sequence analysis of an mRNA that is present during gastrulation, neurulation and tailbud formation reveals that it encodes a novel serine protease containing a single kringle motif and catalytic domain. The spatial expression of this gene, designated Hmserp1, is restricted to precursor cells of the epidermis. The structure and expression of Hmsery1 is discussed in relation to possible functions during development.

Dipeptidyl-peptidase II and cathepsin B activities in amelogenesis of the rat incisor

A body of published evidence suggests that a significant portion of enamel matrix protein synthesized by ameloblasts localises in the lysosomal-endosomal organelles of these enamel organ cells. Little is known regarding the lysosomal proteolytic activities during amelogenesis. The aims of this study were to detect and measure the activities of lysosomal peptidases cathepsin B (E.C. 3.4.22.1) and dipeptidyl-peptidase II (E.C. 3.4.14.2) in the enamel organ of the rat incisor and to ascertain whether rat enamel matrix proteins are degraded by these peptidases in vitro. Whole enamel organs were dissected from rat mandibular incisors. Enamel protein was also collected from the rat teeth. Analysis indicated that the rat incisor enamel organs contained specific activities of both dipeptidyl-peptidase II and cathepsin B at levels comparable with those of kidney which is rich in both these lysosomal peptidases. Gel electrophoresis and immunoblotting demonstrated that both cathepsin B and dipeptidyl-peptidase II were able to substantially degrade the rat enamel proteins in vitro. Based on these observations, we propose that lysosomal proteases have roles in amelogenesis in the intracellular degradation of amelogenins.