Vania Ferreira Prado

Although STIP1 is expressed in the heart and known for neuroprotection, its cardiac role remains undefined. We show that STIP1 is reduced in failing human hearts and that its deficiency in mice impairs resilience to adrenergic overload. Mechanistically, STIP1 loss disrupts the protein synthesis required for cardiomyocyte hypertrophy, positioning this co-chaperone as a hub of the heart’s adaptive response to injury. Clinically, reduced STIP1 in heart failure may worsen dysfunction, underscoring its relevance to disease.

Understanding how α-synuclein misfolding and spreading affect brain systems is central to synucleinopathy research, yet evidence from primate models remains limited. Here, we combined histology, awake structural MRI, awake resting-state fMRI, regional homogeneity, actimetry and touchscreen behavioral testing to longitudinally track the consequences of striatal α-synuclein seeding in the common marmoset. Phosphorylated α-synuclein inclusions were detected from 2 months post-injection and spread progressively to distributed cortical and subcortical regions bilaterally, accompanied by regionally specific structural atrophy. Functional imaging revealed widespread disruption of large-scale networks, particularly within fronto-limbic circuits, alongside reductions in local functional coherence. Despite the absence of overt motor or sleep deficits, animals exhibited a selective impairment in cognitive flexibility, with preserved learning and task engagement. These findings indicate that striatal α-synuclein seeding induces a multi-scale reorganization of brain networks preferentially affecting circuits supporting cognitive flexibility and limbic processing, establishing a primate platform for studying early stages of synucleinopathy.

Background: Stress-inducible phosphoprotein 1 (STIP1) is a co-chaperone involved in neuronal proteostasis and stress resilience. Although expressed in the heart, its role remains undefined. We assessed whether STIP1 deficiency impacts cardiac physiology and stress responses.Methods: STIP1 expression was analyzed in cardiac tissue from heart failure patients. Haploinsufficient STIP1 mice (STIP1+/−) received 7 days of isoproterenol (ISO) to induce cardiac injury, followed by proteomics, histology, and western blot analysis. In vitro, neonatal rat cardiomyocytes (NRCMs) underwent STIP1 or prion protein (PrPC) silencing and were evaluated using molecular assays and total internal reflection fluorescence (TIRF) microscopy.Results: STIP1 levels were reduced in cardiac tissue from heart failure patients, a pattern mirrored in STIP1+/- mice. While STIP1+/- hearts developed normally, ISO exposure led to increased inflammation and fibrosis compared with wild-type. Despite elevated injury markers, STIP1+/- cardiomyocytes failed to undergo hypertrophy in response to ISO. Proteomic profiling identified impaired protein synthesis as the dominant signature in STIP1+/-/ISO hearts, explaining the blunted hypertrophic response. To define STIP1´s contribution to hypertrophy, we silenced STIP1 in NRCMs. Recapitulating in vivo findings, STIP1 silencing blocked ISO‑induced hypertrophy, and also inhibited AngII and phenylephrine hypertrophic responses. Consistent with proteomics, ISO failed to increase protein synthesis or eIF4 expression in STIP1-deficient NRCMs. STIP1 localized to exocytic vesicles, consistent with its secretion visualized by TIRF. Co‑immunoprecipitation confirmed its interaction with PrPC. PrPC silencing abrogated ISO- or AngII-induced hypertrophy, phenocopying STIP1-deficiency.Conclusion: STIP1 engages PrPC in cardiomyocytes to form a receptor‑linked axis that drives pathological hypertrophy through protein‑synthesis–dependent mechanisms.

Translating findings from preclinical assessments of cognitive function relevant to synucleinopathies into successful clinical trials poses significant challenges. In this study, we examined the effectiveness of human-relevant touchscreen cognitive assessments in detecting the impact of α-synuclein pathology in a mouse model of synucleinopathy on the emergence of stimulus-response learning impairments as a potential cognitive biomarker. We generated two types of α-synuclein pre-formed fibrils, each displaying distinct biophysical characteristics in vitro and biochemical properties when stereotaxically injected in vivo. These two types of fibrils were capable of triggering impairments in stimulus-response learning in pre-motor, prodromal disease stages, akin to what is observed in humans with synucleinopathy. This work supports the use of touchscreen cognitive assessments in conjunction with robust preclinical rodent models for identifying targets and testing therapeutic strategies for synucleinopathic diseases.

Proteostasis, maintained by a network of molecular chaperones, plays a central role in cell biology, and has emerged as a critical mechanism underlying pluripotency and development. The stress-inducible phosphoprotein 1 (STIP1) is a co-chaperone essential for proteostasis. STIP1 knockout causes embryonic lethality in mice, but its precise function during embryogenesis remains poorly understood. Here, we investigate the role of STIP1 in early development using in silico and cell-based approaches. Single-cell RNA sequencing data reveals that Stip1 is co-expressed with pluripotency genes in mouse embryos, suggesting a role in stem cell maintenance. To test this, we generated mouse embryonic stem cells (mESCs) from genetically modified mice with altered Stip1/STIP1 expression. STIP1 depletion in mESCs decreases the expression of pluripotency markers, reduces proliferation, and induces apoptosis and genomic instability, whereas its overexpression enhances pluripotency markers expression, promotes proliferation, and confers protection against cellular stress. Moreover, proteins involved in cell cycle progression and DNA damage response are differentially regulated in mESCs, depending on STIP1 levels. Our findings highlight STIP1 as a pivotal regulator of the pluripotent phenotype, early embryogenesis, and cellular resilience, advancing our understanding of proteostasis in stem cell biology and organismal development, with potential implications for disease modeling and regenerative medicine.

Amyotrophic lateral sclerosis (ALS) is a disease influenced by a complex interplay of age, genetics, and sex. Most ALS cases are sporadic, and individuals with this disease show elevated levels of TDP‐43 in their central nervous system and aggregated cytoplasmic inclusions containing TDP‐43 in neurons. Misfolded and aggregated proteins like TDP‐43 can be refolded or marked for degradation by molecular chaperones and their co‐chaperone partners. In this study, we use a mouse model of ALS that mildly overexpresses human wild‐type TDP‐43 in neurons to explore how aging affects the onset of motor abnormalities and proteinopathy in male and female mice. We found that the age‐dependent onset of motor symptoms is more pronounced in male mice, despite both sexes sharing similar TDP‐43 pathology. Further, we found that reducing the activity of STI1, an Hsp90 co‐chaperone, was associated with reduced mislocalized TDP‐43 in the brain and spinal cord and partially rescued some motor deficits. By contrast, overexpressing STI1 seemed to be deleterious, exacerbating the levels of C‐terminal TDP‐43 fragments in the cytoplasm, worsening motor abnormalities and reducing lifespan. Our findings reveal that sex is a key biological factor in an ALS mouse model of TDP‐43 overexpression and provide novel insights on the role of STI1 and proteostasis in mediating TDP‐43 pathology. image

Astrocytes sense and modify neuronal activity, and accumulating evidence suggests a role for these cells in the modulation of neuroinflammation and cognition. Most experiments investigating the in vivo role of astrocytic signaling use viral vectors to drive astrocyte-specific expression of receptors in localized regions of the brain. However, viral vector-mediated delivery of receptors can lead to off-target inflammation and impact neurogenesis, neuronal function and behavior. Here, we used transgenic mice expressing Cre-inducible hM3Dq, a designer receptor exclusively activated by designer drugs (DREADD), to target the Gq-coupled receptor hM3Dq specifically in astrocytes without the use of viral transduction. We showed that in vitro administration of clozapine N-oxide to primary astrocytes derived from astro-hM3Dq mice increased intracellular calcium levels. Similarly, acute in vivo activation of astrocytic hM3Dq induced time-dependent changes in resting-state brain function as well as increased c-Fos expression throughout the brain. Acute astrocyte-specific hM3Dq activation increased synthesis of cortical mRNA of proinflammatory cytokines TNF, IL-1β and IL-6, while chronic activation did not greatly impact proinflammatory cytokine expression. Importantly, however, acute global activation of astrocyte-specific hM3Dq did not adversely affect behavior in a battery of tasks. Taken together, we conclude that the astro-hM3Dq mouse line can serve as a reliable model for studying the brain-wide role of astrocytic muscarinic and Gq signaling in neuroinflammation, behavior and neuronal activity, mitigating the potential negative effects associated with the use of viral transduction.

Alzheimer's disease is a debilitating neurodegenerative condition characterized by amyloid beta plaques and tau neurofibrillary tangles, which leads to progressive cognitive decline. Several new mouse models of fast amyloid deposition have been generated with compound mutations, but how these affect high‐level cognitive function is still not fully understood. Four cohorts of a second‐generation amyloid precursor protein knock‐in mouse model, App^{NL‐G‐F/NL‐G‐F}, which develops aggressive amyloidopathy, were compared with two different control groups that do not produce plaques (App^NL/NL and wildtype littermates), on touchscreen‐based tests of learning and cognitive flexibility. App^{NL‐G‐F/NL‐G‐F} mice learned to discriminate between two visual stimuli during the pairwise visual discrimination (PVD) task but were impaired when the reward contingencies were reversed (the PVR task). Analyses of the correction trials indicated perseverative behavior. One cohort was further tested on the touchscreen Extinction test, which isolates the ability to withhold responding to a previously rewarded stimulus. The App^{NL‐G‐F/NL‐G‐F} mice extinguished their responding no differently than the App^NL/NL control group. These results indicate that compound mutations in App driving fast accumulation of plaques in this mouse model impair cognitive flexibility and may serve as a preclinical target for putative therapeutic drugs.

Synaptic dysfunction is a hallmark of Alzheimer’s disease (AD). Yet due to their plasticity, synapses may also adapt to early AD pathology. Here, we demonstrate that cholinergic neurons mount a presynaptic response to tau pathology in the living human brain. Using multi-tracer positron emission tomography in cognitively normal older adults at risk for AD, we observe that cholinergic neurons increase presynaptic vesicular acetylcholine transporter (VAChT) protein levels when colocalized to tau, but not amyloid. Notably, stronger VAChT responses were associated with cognitive resilience over a decade. Whole-brain single-nucleus RNA sequencing in human and mouse tissue reveal that cholinergic neurons are enriched for a plasticity gene-network anchored to the microtubule-associated protein tau ( MAPT ) gene. In mice, forebrain-specific deletion of VAChT impairs cortical plasticity and hippocampal structural integrity. Overall, our findings identify cholinergic synaptic plasticity, and its failure, as a fundamental mechanism of resilience and vulnerability to tau in presymptomatic AD.