Engaging diverse populations in aging research during the COVID-19 pandemic: Lessons learned from four National Institutes of Health funded-Centers.

Background: The COVID-19 pandemic's impact on our personal and professional lives required a rapid adaptation to the evolving health crisis and accumulating social stresses. Established measures to reduce the spread of infection and potential death had a direct effect on ongoing research that involved older adults and underrepresented racial/ethnic groups. Although important to preserve public health, these measures risk further isolation of vulnerable research participant populations and threatened established community partnerships. To address the social and research challenges evolving from the COVID-19 pandemic, four National Institutes of Health funded-Centers that engage with community members to enhance research and advance the science of aging came together to learn from each other's efforts, approaches, and communication with community partners. Methods: Monthly meetings served as a venue to discuss the challenges of engagement with research participants and support community partners during the pandemic. The developed learning community also contributed to recognize and address research staff stress and isolation. We describe how these conversations led our Centers to address unprecedented challenges and sustain community engagement within diverse populations, especially Black/African Americans, Latinos, Middle Eastern/Arab Americans and the oldest-old. Results: The exchange of information resulted in maintaining long standing community relationships and partnerships in the face of the uncertainties generated by the pandemic. The strategies included adapting education programs to reduce risk of infection, recognizing symptoms, promoting vaccination and understanding of the effect of COVID-19 to the brain. Different strategies were used to address the effects of isolation and maintain community engagement. Although new research participant enrollment was a challenge, telephone and virtual visits allowed research participants to remain active in research. Community members participation in virtual learning events was variable, ranging from a dozen to hundreds of participants. Invitations to organize panels about newly developed topics indicated the need for information from trusted sources. Conclusion: In sum, the COVID-19 pandemic re - directed all four Centers' commitment to community service led to developing strategies for social support, which will potentially contribute to transforming public perceptions about research and researchers.

Liquid-Liquid Phase Separation to Study the Association of Proteins in Solution.

Liquid-liquid phase separation (LLPS) is a reversible biological process that contributes to the formation of critical concentration of proteins, forming membraneless compartments that are physiologically and pathologically relevant. Several proteins have been shown to demix into liquid droplets under in vitro crowding conditions. These studies are mainly conducted in isolation using purified recombinant proteins. Recently, we used LLPS to study the association between two proteins that are co-aggregated in Alzheimer's disease brain, tau, and EFhd2. Here, we describe how we used LLPS to determine the molecular components that contribute to the transition of these two proteins from liquid droplets to solid-like structures.

Influence of Care Network Characteristics on Physician Visit Experiences for Black, White, and Hispanic Older Adults With Dementia.

OBJECTIVES: Most older adults with dementia are assisted by multiple caregivers, but the relationship of care network structure with health care access and quality is underexamined. We sought to test the associations of care network characteristics with the physician visit experience for older adults with dementia across diverse racial/ethnic groups. METHODS: We used data on Medicare beneficiaries (aged 65+) with dementia from the National Health and Aging Trends Study (2015-2019) to fit logistic regression models to test associations between physician visit outcomes and (a) size of the potential care network and (b) proportion of potential care network members (PCNMs) currently helping with daily functioning tasks. We also tested for modifications by race/ethnicity. RESULTS: Hispanic respondents had the largest potential care networks (M = 6.89, standard deviation [SD] = 3.58) and the smallest proportion of PCNMs providing help with daily functioning (M = 29.89%, SD = 22.29). In models adjusted for demographics and dementia classification, both network size and proportional involvement of PCNMs were positively associated with the presence of a PCNM and assistance during the visit. Associations remained significant at 4-year follow-up for the presence of PCNM at the visit and were robust to further adjustments for insurance type, income, and health factors. Associations were not modified by race/ethnicity. DISCUSSION: Larger networks and a higher proportion of PCNMs providing assistance predicted caregiver presence and assistance at the physician visit but not access to care. Findings suggest that strengthening care networks early in the disease may support improved health care outcomes for persons with dementia across diverse populations.

Structure and Enzymatic Activity of an Intellectual Disability-Associated Ornithine Decarboxylase Variant, G84R.

Ornithine decarboxylase (ODC) is a rate-limiting enzyme for the synthesis of polyamines (PAs). PAs are required for proliferation, and increased ODC activity is associated with cancer and neural over-proliferation. ODC levels and activity are therefore tightly regulated, including through the ODC-specific inhibitor, antizyme AZ1. Recently, ODC G84R has been reported as a partial loss-of-function variant that is associated with intellectual disability and seizures. However, G84 is distant from both the catalytic center and the ODC homodimerization interface. To understand how G84R modulates ODC activity, we have determined the crystal structure of ODC G84R in both the presence and the absence of the cofactor pyridoxal 5-phosphate. The structures show that the replacement of G84 by arginine leads to hydrogen bond formation of R84 with F420, the last residue of the ODC C-terminal helix, a structural element that is involved in the AZ1-mediated proteasomal degradation of ODC. In contrast, the catalytic center is essentially indistinguishable from that of wildtype ODC. We therefore reanalyzed the catalytic activity of ODC G84R and found that it is rescued when the protein is purified in the presence of a reducing agent to mimic the reducing environment of the cytoplasm. This suggests that R84 may exert its neurological effects not through reducing ODC catalytic activity but through misregulation of its AZ1-mediated proteasomal degradation.

Large-Scale SARS-CoV-2 Testing Utilizing Saliva and Transposition Sample Pooling.

Identification and isolation of contagious individuals along with quarantine of close contacts, is critical for slowing the spread of COVID-19. Large-scale testing in a surveillance or screening capacity for asymptomatic carriers of COVID-19 provides both data on viral spread and the follow-up ability to rapidly test individuals during suspected outbreaks. The COVID-19 early detection program at Michigan State University has been utilizing large-scale testing in a surveillance or screening capacity since fall of 2020. The methods adapted here take advantage of the reliability, large sample volume, and self-collection benefits of saliva, paired with a cost-effective, reagent conserving two-dimensional pooling scheme. The process was designed to be adaptable to supply shortages, with many components of the kits and the assay easily substituted. The processes outlined for collecting and processing SARS-CoV-2 samples can be adapted to test for future viral pathogens reliably expressed in saliva. By providing this blueprint for universities or other organizations, preparedness plans for future viral outbreaks can be developed.

Beta2-adrenoreceptor agonist clenbuterol produces transient decreases in alpha-synuclein mRNA but no long-term reduction in protein.

ß2-adrenoreceptor (ß2AR) agonists have been associated with a decreased risk of developing Parkinson's disease (PD) and are hypothesized to decrease expression of both alpha-synuclein mRNA (Snca) and protein (α-syn). Effects of ß2AR agonist clenbuterol on the levels of Snca mRNA and α-syn protein were evaluated in vivo (rats and mice) and in rat primary cortical neurons by two independent laboratories. A modest decrease in Snca mRNA in the substantia nigra was observed after a single acute dose of clenbuterol in rats, however, this decrease was not maintained after multiple doses. In contrast, α-syn protein levels remained unchanged in both single and multiple dosing paradigms. Furthermore, clenbuterol did not decrease Snca in cultured rat primary cortical neurons, or decrease Snca or α-syn in mice. Additionally, compared to the single-dose paradigm, repeat dosing resulted in substantially lower levels of clenbuterol in plasma and brain tissue in rodents. Based on our observations of a transient decrease in Snca and no effect on α-syn protein in this preclinical study, these data support the conclusion that clenbuterol is not likely a viable disease-modifying strategy for PD.

Structural basis of binding and inhibition of ornithine decarboxylase by 1-amino-oxy-3-aminopropane.

Ornithine decarboxylase (ODC) is the rate-limiting enzyme for the synthesis of polyamines (PAs). PAs are oncometabolites that are required for proliferation, and pharmaceutical ODC inhibition is pursued for the treatment of hyperproliferative diseases, including cancer and infectious diseases. The most potent ODC inhibitor is 1-amino-oxy-3-aminopropane (APA). A previous crystal structure of an ODC-APA complex indicated that APA non-covalently binds ODC and its cofactor pyridoxal 5-phosphate (PLP) and functions by competing with the ODC substrate ornithine for binding to the catalytic site. We have revisited the mechanism of APA binding and ODC inhibition through a new crystal structure of APA-bound ODC, which we solved at 2.49 Šresolution. The structure unambiguously shows the presence of a covalent oxime between APA and PLP in the catalytic site, which we confirmed in solution by mass spectrometry. The stable oxime makes extensive interactions with ODC but cannot be catabolized, explaining APA's high potency in ODC inhibition. In addition, we solved an ODC/PLP complex structure with citrate bound at the substrate-binding pocket. These two structures provide new structural scaffolds for developing more efficient pharmaceutical ODC inhibitors.

EFhd2 brain interactome reveals its association with different cellular and molecular processes.

EFhd2 is a conserved calcium-binding protein that is highly expressed in the central nervous system. We have shown that EFhd2 interacts with tau protein, a key pathological hallmark in Alzheimer's disease and related dementias. However, EFhd2's physiological and pathological functions in the brain are still poorly understood. To gain insights into its physiological function, we identified proteins that co-immunoprecipitated with EFhd2 from mouse forebrain and hindbrain, using tandem mass spectrometry (MS). In addition, quantitative mass spectrometry was used to detect protein abundance changes due to the deletion of the Efhd2 gene in mouse forebrain and hindbrain regions. Our data show that mouse EFhd2 is associated with cytoskeleton components, vesicle trafficking modulators, cellular stress response-regulating proteins, and metabolic proteins. Moreover, proteins associated with the cytoskeleton, vesicular transport, calcium signaling, stress response, and metabolic pathways showed differential abundance in Efhd2(-/-) mice. This study presents, for the first time, an EFhd2 brain interactome that it is associated with different cellular and molecular processes. These findings will help prioritize further studies to investigate the mechanisms by which EFhd2 modulates these processes in physiological and pathological conditions of the nervous system.

Structure of an AMPK complex in an inactive, ATP-bound state.

Adenosine monophosphate (AMP)-activated protein kinase (AMPK) regulates metabolism in response to the cellular energy states. Under energy stress, AMP stabilizes the active AMPK conformation, in which the kinase activation loop (AL) is protected from protein phosphatases, thus keeping the AL in its active, phosphorylated state. At low AMP:ATP (adenosine triphosphate) ratios, ATP inhibits AMPK by increasing AL dynamics and accessibility. We developed conformation-specific antibodies to trap ATP-bound AMPK in a fully inactive, dynamic state and determined its structure at 3.5-angstrom resolution using cryo-electron microscopy. A 180° rotation and 100-angstrom displacement of the kinase domain fully exposes the AL. On the basis of the structure and supporting biophysical data, we propose a multistep mechanism explaining how adenine nucleotides and pharmacological agonists modulate AMPK activity by altering AL phosphorylation and accessibility.

Gut Microbiota Dysbiosis Is Associated with Elevated Bile Acids in Parkinson's Disease.

The gut microbiome can impact brain health and is altered in Parkinson's disease (PD). The vermiform appendix is a lymphoid tissue in the cecum implicated in the storage and regulation of the gut microbiota. We sought to determine whether the appendix microbiome is altered in PD and to analyze the biological consequences of the microbial alterations. We investigated the changes in the functional microbiota in the appendix of PD patients relative to controls (n = 12 PD, 16 C) by metatranscriptomic analysis. We found microbial dysbiosis affecting lipid metabolism, including an upregulation of bacteria responsible for secondary bile acid synthesis. We then quantitatively measure changes in bile acid abundance in PD relative to the controls in the appendix (n = 15 PD, 12 C) and ileum (n = 20 PD, 20 C). Bile acid analysis in the PD appendix reveals an increase in hydrophobic and secondary bile acids, deoxycholic acid (DCA) and lithocholic acid (LCA). Further proteomic and transcriptomic analysis in the appendix and ileum corroborated these findings, highlighting changes in the PD gut that are consistent with a disruption in bile acid control, including alterations in mediators of cholesterol homeostasis and lipid metabolism. Microbially derived toxic bile acids are heightened in PD, which suggests biliary abnormalities may play a role in PD pathogenesis.

Partnering with Middle Eastern/Arab American and Latino Immigrant Communities to Increase Participation in Alzheimer's Disease Research.

Purpose: Recruitment and retention of US ethnic groups traditionally underrepresented in research continues to pose challenges. The Michigan Center for Contextual Factors in Alzheimer's Disease (MCCFAD) engages with two underserved immigrant communities in Michigan - Middle Eastern/Arab Americans in metro-Detroit and Latinos in the Grand Rapids area - to recruit and retain two Participant Resource Pools (PRP). Procedures: We adapt an existing community-based participatory research (CBPR) approach to recruit Middle Eastern/Arab American and Latino adults of all ages for Alzheimer's disease and related dementia (ADRD) research. Using American Community Survey (2014-2018) data, we compare socio-demographic characteristics of Middle Eastern/Arab Americans and Latinos living in Michigan to our PRPs. Assessment tools and community advisory board feedback identified missteps and culturally sensitive solutions. Main Findings: In the first year of MCCFAD activities, 100 Middle Eastern/Arab Americans and 117 Latinos joined the MCCFAD PRPs. Comparisons to state-level data showed that PRP participants were on average older and more likely to be female than the Middle Eastern/Arab American and Latino populations in Michigan. Further, Middle Eastern/Arab Americans in the PRP reported higher education levels while Latinos reported lower education levels than their respective statewide populations. Community partnerships/feedback identified the importance of connecting with community leaders, attending to matters of within-group diversity, as well as language and semantics. Conclusion: Partnership with communities to develop culturally targeted and sensitive community health events can fill a significant gap in addressing ADRD health disparities by establishing sustainable relationships to increase participation in ADRD research.

Validation of recombinant human protein purified from bacteria: An important step to increase scientific rigor.

E. coli is a common host for generating human recombinant proteins in in vitro studies that seek to understand the biochemical and structural properties of proteins and in drug discovery. Validation of this biological resource is crucial to avoid misinterpretations and assay interference. Here, we demonstrate the use of tandem mass spectrometry to detect inadvertent post-translational modifications on human recombinant proteins produced in E. coli. Additionally, we identified co-purified E. coli proteins orthologous to known human interacting proteins. The results confirmed the importance of mass spectrometry in validating bacterial purified recombinant proteins as part of authenticating this key biological resource.

Age of Migration and Cognitive Function Among Older Latinos in the United States.

BACKGROUND: Age of migration has been shown to have a robust association with Latino immigrant health outcomes; however, the relationship between timing of migration and cognition is less understood. OBJECTIVE: To examine associations between race/ethnicity, nativity, age of migration, and cognitive aging among US-born (USB) non-Latino Whites (NLW) and USB and foreign-born Latinos 50 years and older. METHODS: We used longitudinal biennial data from the Health and Retirement Study (HRS; 2006-2014) to fit generalized linear and linear latent growth curve models for: 1) global cognition (Modified Telephone Interview for Cognitive Status; TICS-M); 2) memory and attention subdomains of TICS-M; and 3) cognitive dysfunction. We also tested for sex modifications. RESULTS: In age and sex adjusted models, all Latino subgroups, independent of nativity and age of migration, had lower global and domain-specific cognitive scores and higher propensity of cognitive impairment classification compared to USB-NLWs. Differences between USB Latinos, but not other Latino subgroups, and USB-NLWs remained after full covariate adjustment. Latinas, independent of nativity or age of migration, had poorer cognitive scores relative to NLW females. Differences between all Latinos and USB-NLWs were principally expressed at baseline. Racial/ethnic, nativity, and age of migration grouping was not associated with slope (nor explained variance) of cognitive decline. CONCLUSION: Older US-born Latinos, regardless of sex exhibit poorer cognitive function than older USB-NLWs and foreign-born Latinos. Social determinants that differentially affect cognitive function, particularly those that compensate for education and sex differences among US-born Latinos and foreign-born Latinos, require further exploration.

Glycosylated hemoglobin level, race/ethnicity, and cognition in midlife and early old age.

Empirical evidence linking racial/ethnic differences in glycosylated hemoglobin levels (HbA1c) to cognitive function in midlife and early old age is limited. We use biomarker data from the Health and Retirement Study (HRS, 2006-2014), on adults 50-64 years at baseline (57-73 years by 2014), and fit multinomial logistic regression models to assess the association between baseline HbA1c, cognitive function (using Langa-Weir classifications) and mortality across 8-years. Additionally, we test for modification effects by race/ethnicity. In age- and sex-adjusted models high HbA1c level was associated with lower baseline cognition and higher relative risk ratios (RRR; vs. normal cognition) for cognitive impairment no dementia (CIND; RRR= 2.3; 95%CI=[1.38;3.84]; p<0.01), and dementia (RRR= 4.00; 95%CI=[1.76;9.10]; p<0.01). Adjusting for sociodemographic, behavioral risk factors, and other health conditions explained the higher RRR for CIND and attenuated the RRR for dementia by approximately 30%. HbA1c levels were not linked to the slope of cognitive decline, and we found no evidence of modification effects for HbA1c by race/ethnicity. Targeting interventions for glycemic control in the critical midlife period can protect baseline cognition and buffer against downstream development of cognitive impairment. This can yield important public health benefits and reductions in burdens associated with cognitive impairment, particularly among race/ethnic minorities who are at higher risk for metabolic diseases.

EFhd2 Affects Tau Liquid-Liquid Phase Separation.

The transition of tau proteins from its soluble physiological conformation to the pathological aggregate forms found in Alzheimer's disease and related dementias, is poorly understood. Therefore, understanding the process that modulates the formation of toxic tau oligomers and their conversion to putative neuroprotective neurofibrillary tangles will lead to better therapeutic strategies. We previously identified that EFhd2 is associated with aggregated tau species in AD brains and the coiled-coil domain in EFhd2 mediates the interaction with tau. To further characterize the association between EFhd2 and tau, we examined whether EFhd2 could affect the liquid-liquid phase separation properties of tau under molecular crowding conditions. We demonstrate that EFhd2 alters tau liquid phase behavior in a calcium and coiled-coil domain dependent manner. Co-incubation of EFhd2 and tau in the absence of calcium leads to the formation of solid-like structures containing both proteins, while in the presence of calcium these two proteins phase separate together into liquid droplets. EFhd2's coiled-coil domain is necessary to alter tau's liquid phase separation, indicating that protein-protein interaction is required. The results demonstrate that EFhd2 affects the liquid-liquid phase separation of tau proteins in vitro, suggesting that EFhd2 modulates the structural dynamics of tau proteins.

Tau13 Antibody Preferentially Immunoprecipitates High Molecular Weight Tau Proteins.

The accumulation of tau protein aggregates is a pathological hallmark in Alzheimer's disease (AD) and other neurodegenerative diseases. However, the identity of the toxic tau conformation that propagates and induces neurodegeneration is still unknown. Anti-tau antibodies are a common tool used to differentiate between normal and pathological-associated tau forms or as passive immunotherapy in the quest to interfere with tau-mediated neurodegeneration. Here, we show that Tau13, a tau N-terminal antibody, preferentially enriches high molecular weight tau species produced in a tauopathy mouse model and AD. The data suggest that Tau13 has higher affinity to specific tau conformation presence in higher molecular weight tau species.

A functional proteomics platform to reveal the sequence determinants of lysine methyltransferase substrate selectivity.

Lysine methylation is a key regulator of histone protein function. Beyond histones, few connections have been made to the enzymes responsible for the deposition of these posttranslational modifications. Here, we debut a high-throughput functional proteomics platform that maps the sequence determinants of lysine methyltransferase (KMT) substrate selectivity without a priori knowledge of a substrate or target proteome. We demonstrate the predictive power of this approach for identifying KMT substrates, generating scaffolds for inhibitor design, and predicting the impact of missense mutations on lysine methylation signaling. By comparing KMT selectivity profiles to available lysine methylome datasets, we reveal a disconnect between preferred KMT substrates and the ability to detect these motifs using standard mass spectrometry pipelines. Collectively, our studies validate the use of this platform for guiding the study of lysine methylation signaling and suggest that substantial gaps exist in proteome-wide curation of lysine methylomes.

Tau's Three-Repeat Domain and EFhd2 Co-incubation Leads to Increased Thioflavin Signal.

Aggregation of the protein tau is a pathological hallmark of Alzheimer's disease (AD) and related disorders. However, the molecular mechanisms that lead to tau protein aggregation are still unclear. Previously, we showed that EFhd2 protein is associated with pathological aggregated forms of tau in AD brain. Further, immuno-gold analyses of purified tau aggregates showed that EFhd2 co-localized with filamentous tau structures. We demonstrated that EFhd2's coiled-coil domain is required for its association with tau proteins. However, it is unknown the role that EFhd2 plays in tau aggregation. Here, we show that incubation of K19-tau with substoichiometric amount of EFhd2 promote the formation of amyloid structures in vitro. The result suggests that EFhd2 may play a role in the biogenesis of aggregated tau.

EF Hand Domain Family Member D2 Is Required for T Cell Cytotoxicity.

Programmed cell death 1 (PD-1) is a major coinhibitory receptor and a member of the immunological synapse (IS). To uncover proteins that regulate PD-1 recruitment to the IS, we searched for cytoskeleton-related proteins that also interact with PD-1 using affinity purification mass spectrometry. Among these proteins, EF hand domain family member D2 (EFHD2), a calcium binding adaptor protein, was functionally and mechanistically analyzed for its contribution to PD-1 signaling. EFHD2 was required for PD-1 to inhibit cytokine secretion, proliferation, and adhesion of human T cells. Interestingly, EFHD2 was also required for human T cell-mediated cytotoxicity and for mounting an antitumor immune response in a syngeneic murine tumor model. Mechanistically, EFHD2 contributed to IS stability, lytic vesicles trafficking, and granzyme B secretion. Altogether, EFHD2 is an important regulator of T cell cytotoxicity and further studies should evaluate its role in T cell-mediated inflammation.

Ezrin Expression is Increased During Disease Progression in a Tauopathy Mouse Model and Alzheimer's Disease.

BACKGROUND: The lack of diagnostic tools and disease-modifying treatments against Alzheimer's disease (AD) and related disorders, collectively known as tauopathies, has led to a socioeconomic burden of epidemic proportion. Proteomics approaches can be used to identify novel proteome changes that could help us understand the pathogenesis of tau-related pathological hallmarks and/or cellular stress responses associated with tauopathy. These studies, however, need to be conducted taking into consideration brain region specificity and stage of neurodegeneration in order to provide insights about the pathological role of the identified proteins. METHODS: We used a tauopathy mouse model (JNPL3) that expresses human tau bearing a P301L mutation and develops motor impairment, the severity of which correlates with the increased accumulation of pathological tau. Tissue was dissected from asymptomatic and severely motor impaired JNPL3 mice as well as non-transgenic littermate controls and subjected to two-dimensional gel electrophoresis. Differentially abundant protein spots were identified by tandem mass spectrometry. Postmortem mild cognitive impairment (MCI), AD and normal aging controls were used to validate the pathological significance of the identified protein. RESULTS: Ezrin was identified as a protein that is upregulated in tau-mediated neurodegeneration. We demonstrate that Ezrin protein abundance increased in JNPL3 mice preceded motor impairment and was sustained in severely motor impaired mice. Ezrin expression was also increased in the temporal cortex of MCI and AD patients. CONCLUSION: The results demonstrate that increased Ezrin protein abundance changes are associated with the early stages of neurodegeneration in tauopathy models and human disease. Understanding the role of Ezrin in tauopathies such as AD may provide new insights for targeting tau-mediated neurodegeneration.