Relaxed Selection Limits Lifespan by Increasing Mutation Load.

To uncover the selective forces shaping life-history trait evolution across species, we investigate the genomic basis underlying adaptations to seasonal habitat desiccation in African killifishes, identifying the genetic variants associated with positive and relaxed purifying selection in 45 killifish species and 231 wild individuals distributed throughout sub-Saharan Africa. In annual species, genetic drift led to the expansion of nuclear and mitochondrial genomes and caused the accumulation of deleterious genetic variants in key life-history modulating genes such as mtor, insr, ampk, foxo3, and polg. Relaxation of purifying selection is also significantly associated with mitochondrial function and aging in human populations. We find that relaxation of purifying selection prominently shapes genomes and is a prime candidate force molding the evolution of lifespan and the distribution of genetic variants associated with late-onset diseases in different species. VIDEO ABSTRACT.

Ceramide signaling targets the PP2A-like protein phosphatase Sit4p to impair vacuolar function, vesicular trafficking and autophagy in Isc1p deficient cells.

The vacuoles play important roles in cellular homeostasis and their functions include the digestion of cytoplasmic material and organelles derived from autophagy. Conserved nutrient signaling pathways regulate vacuolar function and autophagy, ensuring normal cell and organismal development and aging. Recent evidence implicates sphingolipids in the modulation of these processes, but the impact of ceramide signaling on vacuolar dynamics and autophagy remains largely unknown. Here, we show that yeast cells lacking Isc1p, an orthologue of mammalian neutral sphingomyelinase type 2, exhibit vacuolar fragmentation and dysfunctions, namely decreased Pep4p-mediated proteolysis and V-ATPase activity, which impairs vacuolar acidification. Moreover, these phenotypes are suppressed by downregulation of the ceramide-activated protein phosphatase Sit4p. The isc1Δ cells also exhibit defective Cvt and vesicular trafficking in a Sit4p-dependent manner, ultimately contributing to a reduced autophagic flux. Importantly, these phenotypes are also suppressed by downregulation of the nutrient signaling kinase TORC1, which is known to inhibit Sit4p and autophagy, or Sch9p. These results support a model in which Sit4p functions downstream of Isc1p in a TORC1-independent, ceramide-dependent signaling branch that impairs vacuolar function and vesicular trafficking, leading to autophagic defects in yeast.

Mitochondria shed their outer membrane in response to infection-induced stress.

The outer mitochondrial membrane (OMM) is essential for cellular homeostasis. Yet little is known of the mechanisms that remodel it during natural stresses. We found that large "SPOTs" (structures positive for OMM) emerge during Toxoplasma gondii infection in mammalian cells. SPOTs mediated the depletion of the OMM proteins mitofusin 1 and 2, which restrict parasite growth. The formation of SPOTs depended on the parasite effector TgMAF1 and the host mitochondrial import receptor TOM70, which is required for optimal parasite proliferation. TOM70 enabled TgMAF1 to interact with the host OMM translocase SAM50. The ablation of SAM50 or the overexpression of an OMM-targeted protein promoted OMM remodeling independently of infection. Thus, Toxoplasma hijacks the formation of SPOTs, a cellular response to OMM stress, to promote its growth.

Contact and competition between mitochondria and microbes.

Invading microbes occupy the host cytosol and take up nutrients on which host organelles are also dependent. Thus, host organelles are poised to interact with intracellular microbes. Despite the essential role of host mitochondria in cellular metabolic homeostasis and in mediating cellular responses to microbial infection, we know little of how these organelles interact with intracellular pathogens, and how such interactions affect disease pathogenesis. Here, we give an overview of the different classes of physical and metabolic interactions reported to occur between mitochondria and eukaryotic pathogens. Investigating the underlying molecular mechanisms and functions of such interactions will reveal novel aspects of infection biology.

Autophagy determines mtDNA copy number dynamics during starvation.

Derived from bacterial ancestors, mitochondria have maintained their own albeit strongly reduced genome, mitochondrial DNA (mtDNA), which encodes for a small and highly specialized set of genes. MtDNA exists in tens to thousands of copies packaged in numerous nucleoprotein complexes, termed nucleoids, distributed throughout the dynamic mitochondrial network. Our understanding of the mechanisms of how cells regulate the copy number of mitochondrial genomes has been limited. Here, we summarize and discuss our recent findings that Mip1/POLG (mitochondrial DNA polymerase gamma) critically controls mtDNA copy number by operating in 2 opposing modes, synthesis and, unexpectedly, degradation of mtDNA, when yeast cells face nutrient starvation. The balance of the 2 modes of Mip1/POLG and thus mtDNA copy number dynamics depends on the integrity of macroautophagy/autophagy, which sustains continuous synthesis and maintenance of mtDNA. In autophagy-deficient cells, a combination of nucleotide insufficiency and elevated mitochondrial ROS production impairs mtDNA synthesis and drives mtDNA degradation by the 3'-5'-exonuclease activity of Mip1/POLG resulting in mitochondrial genome depletion and irreversible respiratory deficiency. Abbrivations: mtDNA: mitochondrial DNA; mtDCN: mitochondrial DNA copy number.

Autophagy balances mtDNA synthesis and degradation by DNA polymerase POLG during starvation.

Mitochondria contain tens to thousands of copies of their own genome (mitochondrial DNA [mtDNA]), creating genetic redundancy capable of buffering mutations in mitochondrial genes essential for cellular function. However, the mechanisms regulating mtDNA copy number have been elusive. Here we found that DNA synthesis and degradation by mtDNA polymerase γ (POLG) dynamically controlled mtDNA copy number in starving yeast cells dependent on metabolic homeostasis provided by autophagy. Specifically, the continuous mtDNA synthesis by POLG in starving wild-type cells was inhibited by nucleotide insufficiency and elevated mitochondria-derived reactive oxygen species in the presence of autophagy dysfunction. Moreover, after prolonged starvation, 3'-5' exonuclease-dependent mtDNA degradation by POLG adjusted the initially increasing mtDNA copy number in wild-type cells, but caused quantitative mtDNA instability and irreversible respiratory dysfunction in autophagy-deficient cells as a result of nucleotide limitations. In summary, our study reveals that mitochondria rely on the homeostatic functions of autophagy to balance synthetic and degradative modes of POLG, which control copy number dynamics and stability of the mitochondrial genome.

Estratégias para a continuidade das imunizações durante a pandemia de COVID-19 em Tucuruí, PA / Strategies for continuing immunizations during the COVID-19 pandemic in Tucuruí, PA / Estrategias para continuar con las inmunizaciones durante la pandemia COVID-19 en Tucuruí, PA

Objetivo: relatar as estratégias criadas para a continuidade do processo de imunização para a influenza e o sarampo, durante a pandemia de Covid-19, em uma cidade do interior do Pará. Métodos: trata-se de um estudo descritivo, do tipo Relato de Experiência acerca da realização de estratégias para o aumento da cobertura vacinal de Influenza e Sarampo no município de Tucuruí, interior do estado do Pará. As ações foram organizadas e desenvolvidas pela Coordenação Municipal de Imunização e Unidades Básicas de Saúde (UBS) de Tucuruí. Resultados: foram criados protocolos para o trabalho em meio a pandemia, houve a organização das UBS para a vacinação, aconteceram momentos de vacinação em domicílio, foram realizados dias de vacinação massiva. Ainda, por meio de programas de rádio e de TV, foi feita educação em saúde acerca da importância da imunização. Conclusão: a experiência fora bem-sucedida ao alcançar seu público, superando barreiras impostas pela pandemia.(AU)

Objective: to report the strategies created for the continuation of the immunization process for influenza and measles, during the Covid-19 pandemic, in a city in the interior of Pará. Methods: it is a descriptive study, of the type Experience on carrying out strategies to increase the vaccination coverage of Influenza and Measles in the municipality of Tucuruí, in the interior of the state of Pará. The actions were organized and developed by the Municipal Coordination of Immunization and Basic Health Units (BHU) of Tucuruí. Results: protocols were created for work in the midst of a pandemic, there was the organization of BHU for vaccination, there were moments of vaccination at home, days of massive vaccination were carried out. Also, through radio and TV programs, health education was carried out on the importance of immunization. Conclusion: the experiment had been successful in reaching its audience, overcoming barriers imposed by the pandemic.(AU)

Objetivo: reportar las estrategias creadas para la continuación del proceso de inmunización contra influenza y sarampión, durante la pandemia Covid-19, en una ciudad del interior de Pará. Métodos: es un estudio descriptivo, del tipo Experiencia en la realización de estrategias para incrementar la cobertura de vacunación de Influenza y Sarampión en el municipio de Tucuruí, en el interior del estado de Pará Las acciones fueron organizadas y desarrolladas por la Coordinación Municipal de Inmunización y Unidades Básicas de Salud (UBS) de Tucuruí. Resultados: se elaboraron protocolos para trabajar en medio de una pandemia, se organizó la UBS para la vacunación, hubo momentos de vacunación en el domicilio, se realizaron jornadas de vacunación masiva. Asimismo, a través de programas de radio y televisión se realizó educación en salud sobre la importancia de la inmunización. Conclusión: el experimento había logrado llegar a su audiencia, superando las barreras impuestas por la pandemia.(AU)

Ceramide signalling impinges on Sit4p and Hog1p to promote mitochondrial fission and mitophagy in Isc1p-deficient cells.

Mitochondria function as the powerhouses of the cell for energy conversion through the oxidative phosphorylation process. Accumulation of dysfunctional mitochondria promotes a bioenergetic crisis and cell death by apoptosis. Yeast cells lacking Isc1p, an orthologue of mammalian neutral sphingomyelinase type 2, exhibit mitochondrial dysfunction and shortened lifespan associated with the accumulation of specific ceramide species and activation of the PP2A-like protein phosphatase Sit4p and of the Hog1p kinase. Here, we show that isc1Δ cells display hyperactivation of mitophagy that is suppressed by downregulating Sit4p, Hog1p or the TORC1-Sch9p pathway. Notably, isc1Δ cells also have high levels of Dnm1p associated with unbalanced mitochondrial fission, leading to mitochondrial fragmentation, and DNM1 deletion suppressed the oxidative stress sensitivity and shortened lifespan of isc1Δ cells. Moreover, Isc1p and Dnm1p physically interact, suggesting a possible regulatory role for Isc1p in mitochondrial dynamics. Overall, our work demonstrates that Isc1p-mediated ceramide signalling regulates mitophagy and mitochondrial dynamics in yeast with impact on mitochondrial function and lifespan. Since ceramides have been implicated in ageing and diseases associated with mitochondrial dysfunction, our findings suggest that therapeutic strategies targeting ceramide signalling may improve mitochondrial function and human healthspan.

Reduced TORC1 signaling abolishes mitochondrial dysfunctions and shortened chronological lifespan of Isc1p-deficient cells.

The target of rapamycin (TOR) is an important signaling pathway on a hierarchical network of interacting pathways regulating central biological processes, such as cell growth, stress response and aging. Several lines of evidence suggest a functional link between TOR signaling and sphingolipid metabolism. Here, we report that the TORC1-Sch9p pathway is activated in cells lacking Isc1p, the yeast orthologue of mammalian neutral sphingomyelinase 2. The deletion of TOR1 or SCH9 abolishes the premature aging, oxidative stress sensitivity and mitochondrial dysfunctions displayed by isc1Δ cells and this is correlated with the suppression of the autophagic flux defect exhibited by the mutant strain. The protective effect of TOR1 deletion, as opposed to that of SCH9 deletion, is not associated with the attenuation of Hog1p hyperphosphorylation, which was previously implicated in isc1Δ phenotypes. Our data support a model in which Isc1p regulates mitochondrial function and chronological lifespan in yeast through the TORC1-Sch9p pathway although Isc1p and TORC1 also seem to act through independent pathways, as isc1Δtor1Δ phenotypes are intermediate to those displayed by isc1Δ and tor1Δ cells. We also provide evidence that TORC1 downstream effectors, the type 2A protein phosphatase Sit4p and the AGC protein kinase Sch9p, integrate nutrient and stress signals from TORC1 with ceramide signaling derived from Isc1p to regulate mitochondrial function and lifespan in yeast. Overall, our results show that TORC1-Sch9p axis is deregulated in Isc1p-deficient cells, contributing to mitochondrial dysfunction, enhanced oxidative stress sensitivity and premature aging of isc1Δ cells.

HPV knowledge and vaccine acceptance in an uninsured Hispanic population in Providence, RI.

The Food and Drug Administration has approved two human papillomavirus (HPV) vaccines for use by men and women in the United States. The vaccines not only protect against HPV infection, but also reduce the risk of cervical cancer in women. Despite the widespread availability of these vaccines, vulnerable populations such as those with low incomes have been reported to have limited access to and knowlege about HPV vaccines. In order to evaluate and improve HPV vaccination uptake in a population of uninsured, low-income Spanish- speaking individuals attending a free clinic in Rhode Island, we administered a questionnaire regarding knowledge, attitudes, and practices (KAP) and performed an education intervention. We found that knowledge of HPV infection and cervical cancer among the patients sampled was low when comparing Hispanics to non-Hispanics (47.2%, 85.7%, respectively) but willingness to vaccinate oneself or one's child was very high after a brief video- based intervention.