133 research outputs found
Mena/VASP and αII-Spectrin complexes regulate cytoplasmic actin networks in cardiomyocytes and protect from conduction abnormalities and dilated cardiomyopathy
BACKGROUND: In the heart, cytoplasmic actin networks are thought to have important roles in mechanical support, myofibrillogenesis, and ion channel function. However, subcellular localization of cytoplasmic actin isoforms and proteins involved in the modulation of the cytoplasmic actin networks are elusive. Mena and VASP are important regulators of actin dynamics. Due to the lethal phenotype of mice with combined deficiency in Mena and VASP, however, distinct cardiac roles of the proteins remain speculative. In the present study, we analyzed the physiological functions of Mena and VASP in the heart and also investigated the role of the proteins in the organization of cytoplasmic actin networks.
RESULTS: We generated a mouse model, which simultaneously lacks Mena and VASP in the heart. Mena/VASP double-deficiency induced dilated cardiomyopathy and conduction abnormalities. In wild-type mice, Mena and VASP specifically interacted with a distinct αII-Spectrin splice variant (SH3i), which is in cardiomyocytes exclusively localized at Z- and intercalated discs. At Z- and intercalated discs, Mena and β-actin localized to the edges of the sarcomeres, where the thin filaments are anchored. In Mena/VASP double-deficient mice, β-actin networks were disrupted and the integrity of Z- and intercalated discs was markedly impaired.
CONCLUSIONS: Together, our data suggest that Mena, VASP, and αII-Spectrin assemble cardiac multi-protein complexes, which regulate cytoplasmic actin networks. Conversely, Mena/VASP deficiency results in disrupted β-actin assembly, Z- and intercalated disc malformation, and induces dilated cardiomyopathy and conduction abnormalities
SUBARU Near-Infrared Imaging Polarimetry of Misaligned Disks Around The SR24 Hierarchical Triple System
The SR24 multi-star system hosts both circumprimary and circumsecondary
disks, which are strongly misaligned from each other. The circumsecondary disk
is circumbinary in nature. Interestingly, both disks are interacting, and they
possibly rotate in opposite directions. To investigate the nature of this
unique twin disk system, we present 0.''1 resolution near-infrared polarized
intensity images of the circumstellar structures around SR24, obtained with
HiCIAO mounted on the Subaru 8.2 m telescope. Both the circumprimary disk and
the circumsecondary disk are resolved and have elongated features. While the
position angle of the major axis and radius of the NIR polarization disk around
SR24S are 55 and 137 au, respectively, those around SR24N are
110 and 34 au, respectively. With regard to overall morphology, the
circumprimary disk around SR24S shows strong asymmetry, whereas the
circumsecondary disk around SR24N shows relatively strong symmetry. Our NIR
observations confirm the previous claim that the circumprimary and
circumsecondary disks are misaligned from each other. Both the circumprimary
and circumsecondary disks show similar structures in CO observations in
terms of its size and elongation direction. This consistency is because both
NIR and CO are tracing surface layers of the flared disks. As the radius
of the polarization disk around SR24N is roughly consistent with the size of
the outer Roche lobe, it is natural to interpret the polarization disk around
SR24N as a circumbinary disk surrounding the SR24Nb-Nc system.Comment: 14 pages, 5 figures, accepted for publication in A
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