The human dopamine transporter (DAT1) gene contains a variable number of tandem repeats (VNTR) in its 3'-untranslated region (UTR). The linkage and association between the VNTR polymorphism of DAT1 and various neuropsychiatric disorders have been reported. We have determined the genomic structure of DAT1 genes containing 7-, 9-, 10-, and 11-repeat alleles and examined the effect of VNTR polymorphism in the 3'-UTR region of DAT1 on gene expression using the luciferase reporter system in COS-7 cells. Luciferase expression was significantly higher when the 3'-UTR of the DAT1 gene contained the 10-repeat allele than when it contained the 7- or 9-repeat alleles. This suggests that VNTR polymorphism affects the expression of the dopamine transporter.

In this study, we isolated a 25-kDa novel snake venom protein, designated ablomin, from the venom of the Japanese Mamushi snake (Agkistrodon blomhoffi). The amino-acid sequence of this protein was determined by peptide sequencing and cDNA cloning. The deduced sequence showed high similarity to helothermine from the Mexican beaded lizard (Heloderma horridum horridum), which blocks voltage-gated calcium and potassium channels, and ryanodine receptors. Ablomin blocked contraction of rat tail arterial smooth muscle elicited by high K + -induced depolarization in the 0.1-1 lM range, but did not block caffeine-stimulated contraction. Furthermore, we isolated three other proteins from snake venoms that are homologous to ablomin and cloned the corresponding cDNAs. Two of these homologous proteins, triflin and latisemin, also inhibited high K + -induced contraction of the artery. These results indicate that several snake venoms contain novel proteins with neurotoxin-like activity.Keywords: snake venom; neurotoxin; helothermine; cysteinerich secretory proteins; ablomin.Over the past 30 years, a plethora of toxins have been isolated from poisonous organisms, such as snakes, scorpions, spiders, and micro-organisms. These natural toxins use a variety of approaches to arrest the homeostatic mechanisms of other living organisms, including disruption of intracellular signal transduction and cytoskeleton organization [1][2][3][4], and activation or inhibition of blood coagulation factors [5][6][7][8][9][10]. Toxins that block synaptic transmission, called neurotoxins, are widely distributed in venoms. These toxins include the conotoxins from cone snails, agatoxins from spiders, and scorpion toxins [11][12][13][14][15][16]. These toxins exert their potentially lethal effects by specifically and potently blocking a variety of ion channels, including those that conduct Na + , K + , and Ca 2+ . Therefore, neurotoxins have been employed as useful tools to investigate the structure and function of these ion channels [17][18][19][20]. A large number of neurotoxin families have also been found in the venom of Elapidae snakes. These toxins, the a-neurotoxins [21] (represented by a-bungarotoxin [22,23], a-cobratoxin [24][25][26][27], and erabutoxin [28,29]) potently and specifically prevent nicotinic acetylcholine receptor activation. A second family of snake venom neurotoxins, the dendrotoxins, are homologous to Kunitz-type serine protease inhibitors and act primarily by blocking neuronal K + channels [30,31]. In contrast to the neurotoxin-rich venom from Elapidae snakes, the venom from other deadly snakes, including Viperidae and Colubridae snakes, contain surprisingly few neurotoxins, although some neurotoxic phospholipases have been discovered [32][33][34][35][36].In this report, we describe the isolation of a novel protein, ablomin, from the venom of the Japanese Mamushi snake (Agkistrodon blomhoffi, a member of the Viperidae family). When applied to arterial smooth muscle preparations from rat-tails, ablomin blocks K + -stimulated c...

MDC9, also known as meltrin gamma, is a membrane-anchored metalloprotease. MDC9 contains several distinct protein domains: a signal sequence followed by a prodomain and a domain showing sequence similarity to snake venom metalloproteases, a disintegrin-like domain, a cysteine-rich region, an epidermal-growth-factor-like repeat, a transmembrane domain and a cytoplasmic domain. Here we demonstrate that MDC9 expressed in COS cells is cleaved between the prodomain and the metalloprotease domain. Further, when MDC9 was co-expressed in COS cells with amyloid precursor protein (APP695) and treated with phorbol ester, APP695 was digested exclusively at the alpha-secretory site in MDC9-expressing cells. When an artificial alpha-secretory site mutant was also co-expressed with MDC9 and treated with phorbol ester, APP secreted by alpha-secretase was not increased in conditional medium. Inhibition of MDC9 by a hydroxamate-based metalloprotease inhibitor, SI-27, enhanced beta-secretase cleavage. These results suggest that MDC9 has an alpha-secretase-like activity and is activated by phorbol ester.

Emerin is an inner nuclear membrane protein that is involved in X-linked recessive Emery-Dreifuss muscular dystrophy (X-EDMD). Although the function of this protein is still unknown, we revealed that C-terminus transmembrane domain-truncated emerin (amino acid 1-225) binds to lamin A with higher affinity than lamin C. Screening for the emerin binding protein and immunoprecipitation analysis showed that lamin A binds to emerin specifically. We also used the yeast two-hybrid system to clarify that this interaction requires the top half of the tail domain (amino acid 384-566) of lamin A. Lamin A and lamin C are alternative splicing products of the lamin A/C gene that is responsible for autosomal dominant Emery-Dreifuss muscular dystrophy (AD-EDMD). These results indicate that the emerin-lamin interaction requires the tail domains of lamin A and lamin C. The data also suggest that the lamin A-specific region (amino acids 567-664) plays some indirect role in the difference in emerin-binding capacity between lamin A and lamin C. This is the first report that refers the difference between lamin A and lamin C in the interaction with emerin. These data also suggest that lamin A is important for nuclear membrane integrity.