RESUMO
The mechanisms that control the size and shape of membranes are not well understood, despite the importance of these structures in determining organelle and cell morphology. The prospore membrane, a double lipid bilayer that is synthesized de novo during sporulation in S. cerevisiae, grows to surround the four meiotic products. This membrane determines the shape of the newly formed spores and serves as the template for spore wall deposition. Ultimately, the inner leaflet of the prospore membrane will become the new plasma membrane of the cell upon germination. Here we show that Spo71, a pleckstrin homology domain protein whose expression is induced during sporulation, is critical for the appropriate growth of the prospore membrane. Without SPO71, prospore membranes surround the nuclei but are abnormally small, and spore wall deposition is disrupted. Sporulating spo71Δ cells have prospore membranes that properly localize components to their growing leading edges yet cannot properly localize septin structures. We also found that SPO71 genetically interacts with SPO1, a gene with homology to the phospholipase B gene that has been previously implicated in determining the shape of the prospore membrane. Together, these results show that SPO71 plays a critical role in prospore membrane development.
Assuntos
Proteínas de Transporte/fisiologia , Membrana Celular/ultraestrutura , Proteínas de Saccharomyces cerevisiae/fisiologia , Saccharomyces cerevisiae/fisiologia , Proteínas de Transporte/química , Proteínas de Transporte/genética , Membrana Celular/genética , Parede Celular/genética , Parede Celular/ultraestrutura , Estrutura Terciária de Proteína , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/ultraestrutura , Proteínas de Saccharomyces cerevisiae/química , Proteínas de Saccharomyces cerevisiae/genética , Septinas/genética , Septinas/metabolismo , Esporos Fúngicos/genética , Esporos Fúngicos/crescimento & desenvolvimentoRESUMO
Angiopoietins were thought to be endothelial cell-specific via the tie2 receptor. We showed that angiopoietin-1 (ang1) also interacts with integrins on cardiac myocytes (CMs) to increase survival. Because ang1 monomers bind and activate integrins (not tie2), we determined their function in vivo. We examined monomer and multimer expressions during physiological and pathological cardiac remodeling and overexpressed ang1 monomers in phenylephrine-induced cardiac hypertrophy. Cardiac ang1 levels (mRNA, protein) increased during postnatal development and decreased with phenylephrine-induced cardiac hypertrophy, whereas tie2 phosphorylations were unchanged. We found that most or all of the changes during cardiac remodeling were in monomers, offering an explanation for unchanged tie2 activity. Heart tissue contains abundant ang1 monomers and few multimers (Western blotting). We generated plasmids that produce ang1 monomers (ang1-256), injected them into mice, and confirmed cardiac expression (immunohistochemistry, RT-PCR). Ang1 monomers localize to CMs, smooth muscle cells, and endothelial cells. In phenylephrine-induced cardiac hypertrophy, ang1-256 reduced left ventricle (LV)/tibia ratios, fetal gene expressions (atrial and brain natriuretic peptides, skeletal actin, beta-myosin heavy chain), and fibrosis (collagen III), and increased LV prosurvival signaling (akt, MAPK(p42/44)), and AMPK(T172). However, tie2 phosphorylations were unchanged. Ang1-256 increased integrin-linked kinase, a key regulator of integrin signaling and cardiac health. Collectively, these results suggest a role for ang1 monomers in cardiac remodeling.
Assuntos
Angiopoietina-1/química , Angiopoietina-1/metabolismo , Cardiomegalia/prevenção & controle , Integrinas/metabolismo , Angiopoietina-1/genética , Animais , Sequência de Bases , Cardiomegalia/induzido quimicamente , Cardiomegalia/genética , Cardiomegalia/metabolismo , Linhagem Celular , Primers do DNA/genética , Células Endoteliais/metabolismo , Sistema de Sinalização das MAP Quinases , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Miócitos Cardíacos/metabolismo , Fenilefrina/toxicidade , Fosforilação , Ligação Proteica , Proteínas Serina-Treonina Quinases/metabolismo , Estrutura Quaternária de Proteína , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Receptor TIE-2/metabolismo , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Remodelação Ventricular/genética , Remodelação Ventricular/fisiologiaRESUMO
In the yeast Saccharomyces cerevisiae, cells undergoing sporulation form prospore membranes to surround their meiotic nuclei. The prospore membranes ultimately become the plasma membranes of the new cells. The putative phospholipase Spo1 and the tandem Pleckstrin Homology domain protein Spo71 have previously been shown to be required for prospore membrane development, along with the constitutively expressed Vps13 involved in vacuolar sorting. Here, we utilize genetic analysis, and find that SPO73 is required for proper prospore membrane shape and, like SPO71, is necessary for prospore membrane elongation. Additionally, similar to SPO71, loss of SPO73 partially suppresses spo1Δ. Spo73 localizes to prospore membranes and complexes with Spo71. We also find that phosphatidylserine localizes to the prospore membrane. Our results suggest a model where SPO71 and SPO73 act in opposition to SPO1 to form and elongate prospore membranes, while VPS13 plays a distinct role in prospore membrane development.
Assuntos
Proteínas de Transporte/metabolismo , Membrana Celular/metabolismo , Proteínas de Saccharomyces cerevisiae/metabolismo , Saccharomyces cerevisiae/metabolismo , Proteínas de Transporte/genética , Técnicas de Silenciamento de Genes , Lisofosfolipase/genética , Lisofosfolipase/metabolismo , Complexos Multiproteicos/metabolismo , Mutação , Fenótipo , Fosfatidilserinas/metabolismo , Ligação Proteica , Transporte Proteico , Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/genética , Esporos FúngicosRESUMO
Heterocellular communication in the heart is an important mechanism for matching circulatory demands with cardiac structure and function, and neuregulins (Nrgs) play an important role in transducing this signal between the hearts' vasculature and musculature. Here, we review the current knowledge regarding Nrgs, explaining their roles in transducing signals between the heart's microvasculature and cardiomyocytes. We highlight intriguing areas being investigated for developing new, Nrg-mediated strategies to heal the heart in acquired and congenital heart diseases, and note avenues for future research.