Smooth muscle myosin heavy chains (MHCs) exist in multiple isoforms. Rabbit smooth muscles contain at least three types of MHC isoforms: SM1 (204 kD), SM2 (200 kD), and SMemb (200 kD). SM1 and SM2 are specific to smooth muscles, but SMemb is a nonmuscle-type MHC abundantly expressed in the embryonic aorta. We recently reported that these three MHC isoforms are differentially expressed in rabbit during normal vascular development and in experimental arteriosclerosis and atherosclerosis. The purpose of this study was to clarify whether expression of human smooth muscle MHC isoforms is regulated in developing arteries and in atherosclerotic lesions. To accomplish this, we have isolated and characterized three cDNA clones from human smooth muscle: SMHC94 (SM1), SMHC93 (SM2), and HSME6 (SMemb). The expression of SM2 mRNA in the fetal aorta was significantly lower as compared with SM1 mRNA, but the ratio of SM2 to SM1 mRNA was increased after birth. SMemb mRNA in the aorta was decreased after birth but appeared to be increased in the aged. To further examine the MHC expression at the histological level, we have developed three antibodies against human SMI, SM2, and SMemb using the isoform-specific sequences of the carboxyl terminal end. Immunohistologically, SMI was constitutively positive from the fetal stage to adulthood in the apparently normal media of the aorta and coronary arteries, whereas SM2 was negative in fetal arteries of the early gestational stage. In human, unlike rabbit, aorta or coronary arteries, SMemb was detected even in the adult. However, smaller-sized arteries, like the vasa vasorum of the aorta or intramyocardial coronary arterioles, were negative for SMemb. Diffuse intimal thickening in the major coronary arteries was found to be composed of smooth muscles, reacting equally to three antibodies for MHC isoforms, but reactivities with anti-SM2 antibody were reduced with aging. With progression of atherosclerosis, intimal smooth muscles diminished the expression of not only SM2 but also SM1, whereas cr-smooth muscle actin was well preserved. We conclude from these results that smooth muscle MHC isoforms are important molecular markers for studying human vascular smooth muscle cell differentiation as well as the cellular mechanisms of atherosclerosis. (Circ Res. 1993;73:1000-1012
Segmented filamentous bacteria (SFB) are noncultivable commensals inhabiting the gut of various vertebrate species and have been shown to induce Th17 cells in mice. We present the complete genome sequences of both rat and mouse SFB isolated from SFB-monocolonized hosts. The rat and mouse SFB genomes each harbor a single circular chromosome of 1.52 and 1.59 Mb encoding 1346 and 1420 protein-coding genes, respectively. The overall nucleotide identity between the two genomes is 86%, and the substitution rate was estimated to be similar to that of the free-living E. coli. SFB genomes encode typical genes for anaerobic fermentation and spore and flagella formation, but lack most of the amino acid biosynthesis enzymes, reminiscent of pathogenic Clostridia, exhibiting large dependency on the host. However, SFB lack most of the clostridial virulence-related genes. Comparative analysis with clostridial genomes suggested possible mechanisms for host responses and specific adaptations in the intestine.
In mammals, approximately 10% of genome sequences correspond to endogenous viral elements (EVEs), which are derived from ancient viral infections of germ cells. Although most EVEs have been inactivated, some open reading frames (ORFs) of EVEs obtained functions in the hosts. However, EVE ORFs usually remain unannotated in the genomes, and no databases are available for EVE ORFs. To investigate the function and evolution of EVEs in mammalian genomes, we developed EVE ORF databases for 20 genomes of 19 mammalian species. A total of 736,771 non-overlapping EVE ORFs were identified and archived in a database named gEVE (http://geve.med.u-tokai.ac.jp). The gEVE database provides nucleotide and amino acid sequences, genomic loci and functional annotations of EVE ORFs for all 20 genomes. In analyzing RNA-seq data with the gEVE database, we successfully identified the expressed EVE genes, suggesting that the gEVE database facilitates studies of the genomic analyses of various mammalian species.Database URL: http://geve.med.u-tokai.ac.jp
Familial amyotrophic lateral sclerosis type 2 (ALS2) is a juvenile autosomal recessive motor neuron disease caused by the mutations in the gene. The gene product, ALS2/alsin, forms a homophilic oligomer and acts as a guanine nucleotide-exchange factor (GEF) for the small GTPase Rab5. This oligomerization is crucial for both Rab5 activation and ALS2-mediated endosome fusion and maturation in cells. Recently, we have shown that pathogenic missense ALS2 mutants retaining the Rab5 GEF activity fail to properly localize to endosomes via Rac1-stimulated macropinocytosis. However, the molecular mechanisms underlying dysregulated distribution of ALS2 variants remain poorly understood. Therefore, we sought to clarify the relationship between intracellular localization and oligomeric states of pathogenic ALS2 variants. Upon Rac family small GTPase 1 (Rac1) activation, all mutants tested moved from the cytosol to membrane ruffles but not to macropinosomes and/or endosomes. Furthermore, most WT ALS2 complexes were tetramers. Importantly, the sizes of an ALS2 complex carrying missense mutations in the N terminus of the regulator of chromosome condensation 1-like domain (RLD) or in-frame deletion in the pleckstrin homology domain were shifted toward higher molecular weight, whereas the C-terminal vacuolar protein sorting 9 (VPS9) domain missense mutant existed as a smaller dimeric or trimeric smaller form. Furthermore, mutagenesis analyses using the RLD protein structure in conjunction with a cycloheximide chase assay disclosed that these missense mutations led to a decrease in protein stability. Collectively, disorganized higher structures of ALS2 variants might explain their impaired endosomal localization and the stability, leading to loss of the ALS2 function.
Ebola virus (EBOV) is extremely virulent, and its glycoprotein is necessary for viral entry. EBOV may adapt to its new host humans during outbreaks by acquiring mutations especially in glycoprotein, which allows EBOV to spread more efficiently. To identify these evolutionary selected mutations and examine their effects on viral infectivity, we used experimental-phylogenetic-structural interdisciplinary approaches. In evolutionary analysis of all available Zaire ebolavirus glycoprotein sequences, we detected two codon sites under positive selection, which are located near/within the region critical for the host-viral membrane fusion, namely alanine-to-valine and threonine-to-isoleucine mutations at 82 (A82V) and 544 (T544I), respectively. The fine-scale transmission dynamics of EBOV Makona variants that caused the 2014-2015 outbreak showed that A82V mutant was fixed in the population, whereas T544I was not. Furthermore, pseudotype assays for the Makona glycoprotein showed that the A82V mutation caused a small increase in viral infectivity compared with the T544I mutation. These findings suggest that mutation fixation in EBOV glycoprotein may be associated with their increased infectivity levels; the mutant with a moderate increase in infectivity will fix. Our findings showed that a driving force for Ebola virus evolution via glycoprotein may be a balance between costs and benefits of its virulence.
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