The role of lysine acetylation in the function of mitochondrial ribosomal protein L12.

Mitochondria play a central role in energy production and cellular metabolism. Mitochondria contain their own small genome (mitochondrial DNA, mtDNA) that carries the genetic instructions for proteins required for ATP synthesis. The mitochondrial proteome, including the mitochondrial transcriptional machinery, is subject to post-translational modifications (PTMs), including acetylation and phosphorylation. We set out to determine whether PTMs of proteins associated with mtDNA may provide a potential mechanism for the regulation of mitochondrial gene expression. Here, we focus on mitochondrial ribosomal protein L12 (MRPL12), which is thought to stabilize mitochondrial RNA polymerase (POLRMT) and promote transcription. Numerous acetylation sites of MRPL12 were identified by mass spectrometry. We employed amino acid mimics of the acetylated (lysine to glutamine mutants) and deacetylated (lysine to arginine mutants) versions of MRPL12 to interrogate the role of lysine acetylation in transcription initiation in vitro and mitochondrial gene expression in HeLa cells. MRPL12 acetyl and deacetyl protein mimics were purified and assessed for their ability to impact mtDNA promoter binding of POLRMT. We analyzed mtDNA content and mitochondrial transcript levels in HeLa cells upon overexpression of acetyl and deacetyl mimics of MRPL12. Our results suggest that MRPL12 single-site acetyl mimics do not change the mtDNA promoter binding ability of POLRMT or mtDNA content in HeLa cells. Individual acetyl mimics may have modest effects on mitochondrial transcript levels. We found that the mitochondrial deacetylase, Sirtuin 3, is capable of deacetylating MRPL12 in vitro, suggesting a potential role for dynamic acetylation controlling MRPL12 function in a role outside of the regulation of gene expression.

Assessing the Role of Post-Translational Modifications of Mitochondrial RNA Polymerase.

The mitochondrial proteome is subject to abundant post-translational modifications, including lysine acetylation and phosphorylation of serine, threonine, and tyrosine. The biological function of the majority of these protein modifications is unknown. Proteins required for the transcription and translation of mitochondrial DNA (mtDNA) are subject to modification. This suggests that reversible post-translational modifications may serve as a regulatory mechanism for mitochondrial gene transcription, akin to mechanisms controlling nuclear gene expression. We set out to determine whether acetylation or phosphorylation controls the function of mitochondrial RNA polymerase (POLRMT). Mass spectrometry was used to identify post-translational modifications on POLRMT. We analyzed three POLRMT modification sites (lysine 402, threonine 315, threonine 993) found in distinct structural regions. Amino acid point mutants that mimic the modified and unmodified forms of POLRMT were employed to measure the effect of acetylation or phosphorylation on the promoter binding ability of POLRMT in vitro. We found a slight decrease in binding affinity for the phosphomimic at threonine 315. We did not identify large changes in viability, mtDNA content, or mitochondrial transcript level upon overexpression of POLRMT modification mimics in HeLa cells. Our results suggest minimal biological impact of the POLRMT post-translational modifications studied in our system.

PAX3-FOXO1 dictates myogenic reprogramming and rhabdomyosarcoma identity in endothelial progenitors.

Fusion-positive rhabdomyosarcoma (FP-RMS) driven by the expression of the PAX3-FOXO1 (P3F) fusion oncoprotein is an aggressive subtype of pediatric rhabdomyosarcoma. FP-RMS histologically resembles developing muscle yet occurs throughout the body in areas devoid of skeletal muscle highlighting that FP-RMS is not derived from an exclusively myogenic cell of origin. Here we demonstrate that P3F reprograms mouse and human endothelial progenitors to FP-RMS. We show that P3F expression in aP2-Cre expressing cells reprograms endothelial progenitors to functional myogenic stem cells capable of regenerating injured muscle fibers. Further, we describe a FP-RMS mouse model driven by P3F expression and Cdkn2a loss in endothelial cells. Additionally, we show that P3F expression in TP53-null human iPSCs blocks endothelial-directed differentiation and guides cells to become myogenic cells that form FP-RMS tumors in immunocompromised mice. Together these findings demonstrate that FP-RMS can originate from aberrant development of non-myogenic cells driven by P3F.

Elevating Mentorship Competency for Sustained Impact via the University of Zambia Mentor Training Program.

The University of Zambia (UNZA) Mentor Training Program is conducted annually to strengthen the mentorship capacity of postgraduate programs for the health professions. This intensive five-session course trains faculty members in the mentorship of students. Established by senior UNZA leaders and US-based collaborators, this program was designed to address gaps in mentorship identified at the institutional level. Faculty facilitators developed the course curriculum and used a train-the-trainer model to ensure program sustainability. Participants were faculty members who mentor PhD and Master of Medicine students. To assess the program's impact, mentors and their mentees completed questionnaires on the mentor's mentoring competencies at the end of the course and 1 year later. Competency scores were compared longitudinally to quantify potential changes in mentoring behaviors. Mentors and mentees alike noted mentor growth in all competency domains from postcourse to 1 year later, providing evidence of a trend toward improvement in mentorship and that the program may have sustainable and positive effects on mentoring behaviors over time. Salient areas of growth corresponded to emphasized topics and discussions, including addressing diversity, aligning expectations, assessing capacities, motivating mentees, and fostering independence. These findings suggest that mentors internalized this content and transferred it to behavior change. The behavior changes may reveal a larger change in the institutional environment around the mentoring of students. The UNZA Mentor Training Program appears to have sustained impact after a year and should bode well for future benefits to students, faculty, and the institution.

High Engagement in Care in a Pediatric Medical Home for Children Impacted By Parental Substance Use.

The opioid epidemic has heavily affected adults of childbearing age, leading to thousands of children impacted by parental substance use. Few programs provide longitudinal support to these children. This article describes an innovative pediatric medical home model for substance-impacted children and their families, at an urban safety-net hospital. The team-based program directly serves children, and also devotes significant resources to parental health and recovery. In the program's first 3 years, 95% of enrollees were engaged in care, meeting the American Academy of Pediatrics' recommended periodicity schedule for preventive health visits. On-time receipt of childhood vaccines ranged from 95% (pneumococcal conjugate) to 100% (human papilloma virus). The program's high engagement in care shows promise in engaging vulnerable families over time. Future work should explore how to engage children from more diverse backgrounds, and should examine whether the model impacts other indicators of health and well-being for children impacted by parental substance use.

Developing capacity for learning community systems: Experiences from the 100 Million Healthier Lives SCALE Initiative.

Introduction: This paper explores the capabilities that contribute to community transformation and the common pathways followed by communities in the 100 Million Healthier Lives SCALE (Spreading Community Accelerators through Learning and Evaluation) initiative in their transformation journeys towards a "Culture of Health". Methods: Funded by the Robert Wood Johnson Foundation (RWJF), from 2016 to 2020, between 18 to 24 community coalitions nationwide participated in SCALE, the goal of which was to co-design, implement, test, and scale up a model called the Community of Solutions (COS) Framework, that built community capacity around a set of skills and behaviors to advance culture change and create sustainable improvement in health, well-being, and equity. We adapted and applied two qualitative research techniques, meta-ethnography and participatory action synthesis, to evaluate SCALE initiative data. Results: Eight concepts emerged that represent the knowledge, capabilities and practices commonly acquired and utilized across the communities. Overall, these concepts emphasize individual and team leadership, quality improvement skills, an intentional focus on equity, and partnerships for spread and sustainment. Concepts were linked into lines of arguments which were unique storylines explaining the transformation pathways. Three stories of the transformation process emerged from the data. Causal Loop Diagrams (CLDs) were created to represent non-linear system relationships and visually capture some of the most important dynamics of the process of transformation. Even with vast heterogeneity among the SCALE communities and the diversity of activities that the communities undertook, our analysis showed there were a few basic principles that undergirded the process of building capability for transformation. Conclusions: The knowledge from our findings should be useful to expand further research and practice in community learning systems.

Synthetic essentiality between PTEN and core dependency factor PAX7 dictates rhabdomyosarcoma identity.

PTEN promoter hypermethylation is nearly universal and PTEN copy number loss occurs in ~25% of fusion-negative rhabdomyosarcoma (FN-RMS). Here we show Pten deletion in a mouse model of FN-RMS results in less differentiated tumors more closely resembling human embryonal RMS. PTEN loss activated the PI3K pathway but did not increase mTOR activity. In wild-type tumors, PTEN was expressed in the nucleus suggesting loss of nuclear PTEN functions could account for these phenotypes. Pten deleted tumors had increased expression of transcription factors important in neural and skeletal muscle development including Dbx1 and Pax7. Pax7 deletion completely rescued the effects of Pten loss. Strikingly, these Pten;Pax7 deleted tumors were no longer FN-RMS but displayed smooth muscle differentiation similar to leiomyosarcoma. These data highlight how Pten loss in FN-RMS is connected to a PAX7 lineage-specific transcriptional output that creates a dependency or synthetic essentiality on the transcription factor PAX7 to maintain tumor identity.

Evidence for the Role of Mitochondrial DNA Release in the Inflammatory Response in Neurological Disorders.

Mitochondria are regarded as the metabolic centers of cells and are integral in many other cell processes, including the immune response. Each mitochondrion contains numerous copies of mitochondrial DNA (mtDNA), a small, circular, and bacterial-like DNA. In response to cellular damage or stress, mtDNA can be released from the mitochondrion and trigger immune and inflammatory responses. mtDNA release into the cytosol or bloodstream can occur as a response to hypoxia, sepsis, traumatic injury, excitatory cytotoxicity, or drastic mitochondrial membrane potential changes, some of which are hallmarks of neurodegenerative and mood disorders. Released mtDNA can mediate inflammatory responses observed in many neurological and mood disorders by driving the expression of inflammatory cytokines and the interferon response system. The current understanding of the role of mtDNA release in affective mood disorders and neurodegenerative diseases will be discussed.

Structure, mechanism, and regulation of mitochondrial DNA transcription initiation.

Mitochondria are specialized compartments that produce requisite ATP to fuel cellular functions and serve as centers of metabolite processing, cellular signaling, and apoptosis. To accomplish these roles, mitochondria rely on the genetic information in their small genome (mitochondrial DNA) and the nucleus. A growing appreciation for mitochondria's role in a myriad of human diseases, including inherited genetic disorders, degenerative diseases, inflammation, and cancer, has fueled the study of biochemical mechanisms that control mitochondrial function. The mitochondrial transcriptional machinery is different from nuclear machinery. The in vitro re-constituted transcriptional complexes of Saccharomyces cerevisiae (yeast) and humans, aided with high-resolution structures and biochemical characterizations, have provided a deeper understanding of the mechanism and regulation of mitochondrial DNA transcription. In this review, we will discuss recent advances in the structure and mechanism of mitochondrial transcription initiation. We will follow up with recent discoveries and formative findings regarding the regulatory events that control mitochondrial DNA transcription, focusing on those involved in cross-talk between the mitochondria and nucleus.

Phosphorylation of mitochondrial transcription factor B2 controls mitochondrial DNA binding and transcription.

Mammalian cells contain genetic information in two compartments, the nucleus and the mitochondria. Mitochondrial gene expression must be coordinated with nuclear gene expression to respond to cellular energetic needs. To gain insight into the coordination between the nucleus and mitochondria, there is a need to understand the regulation of transcription of mitochondrial DNA (mtDNA). Reversible protein post-translational modifications of the mtDNA transcriptional machinery may be one way to control mtDNA transcription. Here we focus on a member of the mtDNA transcription initiation complex, mitochondrial transcription factor B2 (TFB2M). TFB2M melts mtDNA at the promoter to allow the RNA polymerase (POLRMT) to access the DNA template and initiate transcription. Three phosphorylation sites have been previously identified on TFB2M by mass spectrometry: threonine 184, serine 197, and threonine 313. Phosphomimetics were established at these positions. Proteins were purified and analyzed for their ability to bind mtDNA and initiate transcription in vitro. Our results indicate phosphorylation at threonine 184 and threonine 313 impairs promoter binding and prevents transcription. These findings provide a potential regulatory mechanism of mtDNA transcription and help clarify the importance of protein post-translational modifications in mitochondrial function.

Building capacity for Public Health 3.0: introducing implementation science into an MPH curriculum.

BACKGROUND: Many public health programs fail because of an inability to implement tested interventions in diverse, complex settings. The field of implementation science is engaged in developing strategies for successful implementation, but current training is primarily researcher-focused. To tackle the challenges of the twenty-first century, public health leaders are promoting a new model titled Public Health 3.0 where public health practitioners become "chief health strategists" and develop interdisciplinary skills for multisector engagement to achieve impact. This requires broad training for public health practitioners in implementation science that includes the allied fields of systems and design thinking, quality improvement, and innovative evaluation methods. At UNC Chapel Hill's Gillings School of Global Public Health, we created an interdisciplinary set of courses in applied implementation science for Master of Public Health (MPH) students and public health practitioners. We describe our rationale, conceptual approach, pedagogy, courses, and initial results to assist other schools contemplating similar programs. METHODS: Our conceptual approach recognized the vital relationship between implementation research and practice. We conducted a literature review of thought leaders in public health to identify skill areas related to implementation science that are priorities for the future workforce. We also reviewed currently available training programs in implementation science to understand their scope and objectives and to assess whether any of these would be a fit for these priorities. We used a design focused implementation framework to create four linked courses drawing from multiple fields such as engineering, management, and the social sciences and emphasizing application through case studies. We validated the course content by mapping them to implementation science competencies in the literature. RESULTS: To date, there is no other program that provides comprehensive interdisciplinary skills in applied implementation science for MPH students. As of April 2018, we have offered a total of eleven sections of the four courses, with a total enrollment of 142, of whom 127 have been master's-level students in the school of public health. Using Kirkpatrick's Model, we found positive student reaction, learning, and behavior. Many students have completed applied implementation science focused practicums, master's papers, and special studies. CONCLUSIONS: A systematically designed interdisciplinary curriculum in applied implementation science for MPH students has been found by students to be a useful set of skills. Students have demonstrated the capability to master this material and incorporate it into their practicums and master's papers.

The genomic landscape of tuberous sclerosis complex.

Tuberous sclerosis complex (TSC) is a rare genetic disease causing multisystem growth of benign tumours and other hamartomatous lesions, which leads to diverse and debilitating clinical symptoms. Patients are born with TSC1 or TSC2 mutations, and somatic inactivation of wild-type alleles drives MTOR activation; however, second hits to TSC1/TSC2 are not always observed. Here, we present the genomic landscape of TSC hamartomas. We determine that TSC lesions contain a low somatic mutational burden relative to carcinomas, a subset feature large-scale chromosomal aberrations, and highly conserved molecular signatures for each type exist. Analysis of the molecular signatures coupled with computational approaches reveals unique aspects of cellular heterogeneity and cell origin. Using immune data sets, we identify significant neuroinflammation in TSC-associated brain tumours. Taken together, this molecular catalogue of TSC serves as a resource into the origin of these hamartomas and provides a framework that unifies genomic and transcriptomic dimensions for complex tumours.

Kinetic and Structural Basis for Acyl-Group Selectivity and NAD(+) Dependence in Sirtuin-Catalyzed Deacylation.

Acylation of lysine is an important protein modification regulating diverse biological processes. It was recently demonstrated that members of the human Sirtuin family are capable of catalyzing long chain deacylation, in addition to the well-known NAD(+)-dependent deacetylation activity [Feldman, J. L., Baeza, J., and Denu, J. M. (2013) J. Biol. Chem. 288, 31350-31356]. Here we provide a detailed kinetic and structural analysis that describes the interdependence of NAD(+)-binding and acyl-group selectivity for a diverse series of human Sirtuins, SIRT1-SIRT3 and SIRT6. Steady-state and rapid-quench kinetic analyses indicated that differences in NAD(+) saturation and susceptibility to nicotinamide inhibition reflect unique kinetic behavior displayed by each Sirtuin and depend on acyl substrate chain length. Though the rate of nucleophilic attack of the 2'-hydroxyl on the C1'-O-alkylimidate intermediate varies with acyl substrate chain length, this step remains rate-determining for SIRT2 and SIRT3; however, for SIRT6, this step is no longer rate-limiting for long chain substrates. Cocrystallization of SIRT2 with myristoylated peptide and NAD(+) yielded a co-complex structure with reaction product 2'-O-myristoyl-ADP-ribose, revealing a latent hydrophobic cavity to accommodate the long chain acyl group, and suggesting a general mechanism for long chain deacylation. Comparing two separately determined co-complex structures containing either a myristoylated peptide or 2'-O-myristoyl-ADP-ribose indicates there are conformational changes at the myristoyl-ribose linkage with minimal structural differences in the enzyme active site. During the deacylation reaction, the fatty acyl group is held in a relatively fixed position. We describe a kinetic and structural model to explain how various Sirtuins display unique acyl substrate preferences and how different reaction kinetics influence NAD(+) dependence. The biological implications are discussed.

SIRT3 mediates multi-tissue coupling for metabolic fuel switching.

SIRT3 is a member of the Sirtuin family of NAD(+)-dependent deacylases and plays a critical role in metabolic regulation. Organism-wide SIRT3 loss manifests in metabolic alterations; however, the coordinating role of SIRT3 among metabolically distinct tissues is unknown. Using multi-tissue quantitative proteomics comparing fasted wild-type mice to mice lacking SIRT3, innovative bioinformatic analysis, and biochemical validation, we provide a comprehensive view of mitochondrial acetylation and SIRT3 function. We find SIRT3 regulates the acetyl-proteome in core mitochondrial processes common to brain, heart, kidney, liver, and skeletal muscle, but differentially regulates metabolic pathways in fuel-producing and fuel-utilizing tissues. We propose an additional maintenance function for SIRT3 in liver and kidney where SIRT3 expression is elevated to reduce the acetate load on mitochondrial proteins. We provide evidence that SIRT3 impacts ketone body utilization in the brain and reveal a pivotal role for SIRT3 in the coordination between tissues required for metabolic homeostasis.

Quantification of mitochondrial acetylation dynamics highlights prominent sites of metabolic regulation.

Lysine acetylation is rapidly becoming established as a key post-translational modification for regulating mitochondrial metabolism. Nonetheless, distinguishing regulatory sites from among the thousands identified by mass spectrometry and elucidating how these modifications alter enzyme function remain primary challenges. Here, we performed multiplexed quantitative mass spectrometry to measure changes in the mouse liver mitochondrial acetylproteome in response to acute and chronic alterations in nutritional status, and integrated these data sets with our compendium of predicted Sirt3 targets. These analyses highlight a subset of mitochondrial proteins with dynamic acetylation sites, including acetyl-CoA acetyltransferase 1 (Acat1), an enzyme central to multiple metabolic pathways. We performed in vitro biochemistry and molecular modeling to demonstrate that acetylation of Acat1 decreases its activity by disrupting the binding of coenzyme A. Collectively, our data reveal an important new target of regulatory acetylation and provide a foundation for investigating the role of select mitochondrial protein acetylation sites in mediating acute and chronic metabolic transitions.

Calorie restriction and SIRT3 trigger global reprogramming of the mitochondrial protein acetylome.

Calorie restriction (CR) extends life span in diverse species. Mitochondria play a key role in CR adaptation; however, the molecular details remain elusive. We developed and applied a quantitative mass spectrometry method to probe the liver mitochondrial acetyl-proteome during CR versus control diet in mice that were wild-type or lacked the protein deacetylase SIRT3. Quantification of 3,285 acetylation sites-2,193 from mitochondrial proteins-rendered a comprehensive atlas of the acetyl-proteome and enabled global site-specific, relative acetyl occupancy measurements between all four experimental conditions. Bioinformatic and biochemical analyses provided additional support for the effects of specific acetylation on mitochondrial protein function. Our results (1) reveal widespread reprogramming of mitochondrial protein acetylation in response to CR and SIRT3, (2) identify three biochemically distinct classes of acetylation sites, and (3) provide evidence that SIRT3 is a prominent regulator in CR adaptation by coordinately deacetylating proteins involved in diverse pathways of metabolism and mitochondrial maintenance.

Sirtuin catalysis and regulation.

Sirtuins are a family of NAD(+)-dependent protein deacetylases/deacylases that dynamically regulate transcription, metabolism, and cellular stress response. Their general positive link with improved health span in mammals, potential regulation of pathways mediated by caloric restriction, and growing links to human disease have spurred interest in therapeutics that target their functions. Here, we review the current understanding of the chemistry of catalysis, biological targets, and endogenous regulation of sirtuin activity. We discuss recent efforts to generate small-molecule regulators of sirtuin activity.

SIRT3 protein deacetylates isocitrate dehydrogenase 2 (IDH2) and regulates mitochondrial redox status.

Mitochondria play a central role in oxidative energy metabolism and age-related diseases such as cancer. Accumulation of spurious oxidative damage can cause cellular dysfunction. Antioxidant pathways that rely on NADPH are needed for the reduction of glutathione and maintenance of proper redox status. The mitochondrial matrix protein isocitrate dehydrogenase 2 (IDH2) is a major source of NADPH. Previously, we demonstrated that the NAD(+)-dependent deacetylase SIRT3 was essential for the prevention of age-related hearing loss in mice fed a calorically restricted diet. Here we provide direct biochemical and biological evidence establishing an exquisite regulatory relationship between IDH2 and SIRT3 under acute and chronic caloric restriction. The regulated site of acetylation was mapped to Lys-413, an evolutionarily invariant residue. Site-specific, genetic incorporation of N(ε)-acetyllysine into position 413 of IDH2 revealed that acetylated IDH2 displays a dramatic 44-fold loss in activity. Deacetylation by SIRT3 fully restored maximum IDH2 activity. The ability of SIRT3 to protect cells from oxidative stress was dependent on IDH2, and the deacetylated mimic, IDH2(K413R) variant was able to protect Sirt3(-/-) mouse embryonic fibroblasts from oxidative stress through increased reduced glutathione levels. Together these results uncover a previously unknown mechanism by which SIRT3 regulates IDH2 under dietary restriction. Recent findings demonstrate that IDH2 activities are a major factor in cancer, and as such, these results implicate SIRT3 as a potential regulator of IDH2-dependent functions in cancer cell metabolism.

A model for increasing palliative care in the intensive care unit: enhancing interprofessional consultation rates and communication.

BACKGROUND: Only a minority of patients who die in the medical intensive care unit (MICU) receive palliative care services. At the South Texas Veterans Health Care System Audie L. Murphy Hospital, only 5% of patients who died in the MICU from May to August 2010 received a palliative care consultation. MEASURES: We measured the percentage of MICU patients for which there was a palliative care consultation during the intervention period. INTERVENTION: Starting October 1, 2010 and ending April 30, 2011, the palliative care and MICU teams participated in daily "pre-rounds" to identify patients at risk for poor outcomes, who may benefit from a palliative care consultation. OUTCOMES: Palliative care consultation increased significantly from 5% to 59% for patients who died in the MICU during the intervention period. Additionally, palliative care consultation increased from 5% to 21% for all patients admitted to the MICU during the intervention period. CONCLUSIONS/LESSONS LEARNED: Daily pre-rounds between the palliative care and MICU teams increased palliative care services for MICU patients at risk for poor outcomes, who may benefit from a palliative care consultation.

Catalysis and mechanistic insights into sirtuin activation.

SIRT1 is a member of the Sir2 family of NAD(+)-dependent protein deacetylases. The central role of SIRT1 in multiple metabolic and age-related pathways has pushed SIRT1 to the forefront to discover small-molecule activators. Promising compounds, including resveratrol and SRT1720 have been reported, however, whether these compounds are direct activators and the mechanism by which they activate remains poorly defined. This review examines the current debate surrounding purported activators, and will focus on the assays used in screening compounds, sirtuin catalysis, and the mechanistic basis for their actions. We discuss the potential pathways of SIRT1 activation that could be exploited for the development of novel therapeutics for treating type II diabetes, neurodegeneration, and diseases associated with aging.