To investigate the potential role of fluid mechanical factors in the localized genesis and development of atherosclerotic lesions in humans, the exact anatomic locations of atherosclerotic lesions and the flow patterns at such sites in left and right human coronary arteries were studied in detail by flow visualization and high-speed cinemicrographic techniques using five isolated, transparent human coronary arterial trees prepared postmortem. It was found that atherosclerotic plaques and wall thickenings in left and right coronary arteries were localized almost exclusively on the outer wall of one or both daughter vessels at major bifurcations and T-junctions, which left the flow-divider free of lesions, and along the inner wall of curved segments. When flow patterns in such vessels were studied in detail, it was discovered that these sites were where flow was either slow or disturbed with the formation of slow recirculation and secondary flows and where wall shear stress was low. The results indicate that the major hemodynamic factors directly related to the localization of atherosclerotic plaques and wall thickenings in the human arterial system are the low fluid velocity and the resultant low shear stress that acts on the vessel wall.

Syntaxin-1 is a component of the synaptic vesicle docking and/or membrane fusion soluble N-ethylmaleimide-sensitive factor attachment receptor (SNARE) complex (7S and 20S complexes) in nerve terminals. Syntaxin-1 also forms a heterodimer with Munc18/n-Sec1/rbSec1 in a complex that is distinct from the 7S and 20S complexes. In this report, we identify a novel syntaxin-1-binding protein, tomosyn, that is capable of dissociating Munc18 from syntaxin-1 and forming a novel 10S complex with syntaxin-1, soluble N-etyhlmaleimide-sensitive factor attachment (SNAP) 25, and synaptotagmin. The 130 kDa isoform of tomosyn is specifically expressed in brain, where its distribution partly overlaps with that of syntaxin-1 in nerve terminals. High level expression of either syntaxin-1 or tomosyn results in a specific reduction in Ca2+-dependent exocytosis from PC12 cells. These results suggest that tomosyn is an important component in the neurotransmitter release process where it may stimulate SNARE complex formation.

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We puri®ed a novel actin ®lament (F-actin)-binding protein from the soluble fraction of Saccharomyces cerevisiae by successive column chromatographies by use of the 125 I-labeled F-actin blot overlay method. The puri®ed protein showed a minimum M r of about 140 kDa on SDS-polyacrylamide gel electrophoresis and we named it ABP140. A search with the partial amino acid sequences of ABP140 against the Saccharomyces Genome Database revealed that the open reading frame of the ABP140 gene (ABP140) corresponded to YOR239W fused with YOR240W by the +1 translational frame shift. The encoded protein consisted of 628 amino acids with a calculated M r of 71,484. The recombinant protein interacted with F-actin and showed the activity to crosslink F-actin into a bundle. Indirect immuno¯uorescence study demonstrated that ABP140 was colocalized with both cortical actin patches and cytoplasmic actin cables in intact cells. However, elimination of ABP140 by gene disruption did not show a deleterious e ect on cell growth or a ect the organization of F-actin. These results indicate that ABP140 is not required for cell growth but may be involved in the reorganization of F-actin in the budding yeast.

Background: We have recently identi®ed a novel cellcell adhesion system, named NAP system, which is localized at cadherin-based cell-cell adherens junctions (AJs). The NAP system is composed of at least nectin, afadin and ponsin. Nectin is an immunoglobulin-like cell adhesion molecule. Afadin is an actin ®lament-binding protein which associates nectin with the actin cytoskeleton. Ponsin is an afadin-binding protein which furthermore binds to vinculin and provides a possible linkage of nectin-afadin to cadherin-catenin through vinculin. We compared here the behaviour of the NAP and cadherin-catenin systems during the formation and disruption of the polarized junctional alignment in epithelial cells.

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We recently purified and characterized from rat brain a GTPase-activating protein (GAP) specific for the Rab3 small G protein subfamily implicated in Ca 2؉ -dependent exocytosis. Rab3 GAP showed two bands with M r of about 130,000 (p130) and 150,000 (p150) on SDS-polyacrylamide gel electrophoresis. p130, but not p150, showed the catalytic activity. Because p150 was likely the subunit of Rab3 GAP, here we cloned the cDNA of p150, determined its primary structure, and characterized it. The tissue and subcellular distribution patterns of p150 and p130 were similar, and both the proteins were enriched in the synaptic soluble fraction. p150 was co-immunoprecipitated with p130 from this fraction. Recombinant p150 formed a heterodimer with recombinant p130 as estimated by sucrose density gradient ultracentrifugation. Recombinant p150 neither showed the Rab3A GAP activity nor affected the activity of recombinant p130. When p150 and p130 were co-expressed in the cells, the subcellular localization of each protein did not change. These results indicate that p150 is the noncatalytic subunit of Rab3 GAP.