Characterization of the mammalian septin H5: distinct patterns of cytoskeletal and membrane association from other septin proteins.

The mechanisms controlling cytokinesis during yeast budding and animal cell fission appear quite different, yet both require members of the septin protein family. Mammalian homologs of this novel family of GTPases have been identified but little is known about their properties or functions. Using an antibody specific for the mammalian septin H5, we show that this protein is expressed at distinct levels in a variety of tissues. Tissue expression levels in different tissues did not coincide with those of the only previously characterized mammalian septin Nedd5. H5, like Nedd5, localizes to the cleavage furrow in mitotic fibroblast cells but in non-mitotic cells these proteins associate with actin filaments in different ways. Nedd5 predominantly localizes with stress fibers, but only associates with central portions of the microfilament bundles. In contrast, H5 associates with the entire length of the stress fibers and the cortical actin network. Conditions that disrupt the actin cytoskeleton also disrupt the filamentous patterns of both Nedd5 and H5, resulting in a punctate cytoplasmic pattern. Cell fractionation revealed that H5 co-fractionated with actin, while Nedd5 was predominantly restricted to the membrane fraction. Co-immunoprecipitation experiments revealed that although H5 will co-precipitate with Nedd5, the precipitation is not quantitative. Taken together, these results not only show that H5 behaves like a septin, but also demonstrate that individual septin proteins have distinct properties, suggesting that they may play different roles in cytokinesis and in other stages of the cell cycle.

Revascularización coronaria en paciente con Angor Pectoris y Mixedema / Coronary revascularization in a patient with angor pectoris and mixedema

Una mujer portadora de Hipotiroidismo primario severo y una cardiopatía isquémica mostró, luego de instalada la terapeútica con hormonas tiroideas, angor inestable e infarto agudo de miocardio, seguido de angor post-infarto. La cirugía de revascularización miocárdica alivió los síntomas de la cardiopatía isquémica y permitió la terapeútica sustitutiva. Se discuten las indicaciones, los riesgos y las complicaciones de este tipo de cirugía en el hipotiroidismo severo, previo a su control por la terapeútica