Biology subjects

Simoes, S.

Publications and source records attributed to Simoes, S..

6 recordsLinked to original sources

bioRxiv2026

E-cadherin clustering as a regulator of morphogenesis

Cell adhesion enables animal multicellular development. E-cadherin and the cadherin-catenin adhesion complex at adherens junctions are engaged in dynamic interactions with actomyosin generated contractile forces to drive epithelial morphogenesis. However, our understanding of how adhesion is regulated and how the tuning of adhesion contributes to morphogenesis remains incomplete. One key determinant of E-cadherin adhesion strength is clustering of the cadherin-catenin adhesion complex, a property studied extensively in vitro. Here, we use optogenetics to enhance E-cadherin cluster formation in the Drosophila embryo. Enlarged clusters were associated with increased E-cadherin surface abundance, assembled a normal cadherin-catenin complex, and showed reduced membrane mobility and turnover consistent with an increase in cell adhesion strength. Drosophila embryos with enhanced E-cadherin clustering displayed a severe reduction in cell intercalation and convergent extension of the anterior-posterior axis. To account for these observations, we modified existing vertex models to include junction-specific viscous forces representing E-cadherin-mediated friction between cells. This dissipative adhesion model predicts that enhanced adhesion increases resistance to cell rearrangements, thereby reducing cell neighbor exchanges and impairing convergent extension. To test model predictions, we analyzed two types of morphogenetic movements in embryos with enhanced E-cadherin clustering. Neuroblast ingression, which requires both apical constriction and cell rearrangement, was severely slowed. In contrast, mesoderm invagination, which requires apical constriction without neighbor exchanges, proceeded normally. Our findings suggest that optogenetic clustering, in contrast to overexpression of E-cadherin, is a valuable tool to examine the consequences of enhancing adhesion strength in tissue morphogenesis. Moreover, we propose that regulating E-cadherin clustering is essential for movements that require cell-cell contact changes.

cell biology↗

bioRxiv2025

Extracellular matrix mechanical cues (dys)regulate metabolic redox homeostasis due to impaired autophagic flux

Extracellular matrix (ECM) stiffness is increasingly recognized as a critical regulator of cellular behavior, governing processes such as proliferation, differentiation, and metabolism. Neurodegenerative diseases are characterized by mitochondrial dysfunction, oxidative stress, impaired autophagy, and progressive softening of the brain tissue, yet research into how mechanical cues influence cellular metabolism in this context remains scarce. In this study, we evaluated the long-term effects of brain-compliant, soft ECM on mitochondrial bioenergetics, redox balance, and autophagic capacity in neuronal cells. Using human neuroblastoma (SH-SY5Y) and mouse hippocampal (HT22) cell lines, as well as primary mouse neurons, we observed that prolonged exposure to soft ECM resulted in mitochondrial bioenergetic dysfunction, redox imbalance, and disrupted autophagic flux. These findings were consistently validated across both human and mouse neuronal cells. Our data indicate a decreased maximal autophagic capacity in cells exposed to long-term soft ECM, potentially due to an imbalance in autophagosome formation and degradation, as demonstrated by decreased LC3 II levels following chloroquine-induced autophagic flux inhibition. This impairment in autophagy was coupled with increased cellular oxidative stress, further indicating metabolic alterations. These findings emphasize the critical role of ECM stiffness in regulating neuronal cell metabolism and suggest that prolonged exposure to soft ECM may mimic key aspects of neurodegenerative disease pathology, thereby enhancing the physiological relevance of in vitro models. This study underscores the necessity for further research into ECM mechanics as a contributing factor in neurodegenerative disease progression and as a potential target for therapeutic strategies.

cell biology↗

bioRxiv2022

Crumbs complex-directed apical membrane dynamics in epithelial cell ingression

Epithelial cells often leave their tissue context and ingress to form new cell types or acquire migratory ability to move to distant sites during development and tumor progression. Cell lose their apical membrane and epithelial adherens junctions during ingression. However, how factors that organize apical-basal polarity contribute to ingression is unknown. Here, we show that the dynamic regulation of the apical Crumbs polarity complex is crucial for normal neural stem cell ingression. Crumbs endocytosis and recycling allow ingression to occur in a normal timeframe. During early ingression, Crumbs and its complex partner the RhoGEF Cysts support myosin and apical constriction to ensure robust ingression dynamics. During late ingression, the E3-ubiquitin ligase Neuralized facilitates the disassembly of the Crumbs complex and the rapid endocytic removal of the apical cell domain. Our findings reveal a mechanism integrating cell fate, apical polarity, endocytosis, vesicle trafficking, and actomyosin contractility to promote cell ingression, a fundamental morphogenetic process observed in animal development and cancer.

developmental biology↗

bioRxiv2020

Endosomal trafficking is required for glycosylation and normal maturation of the Alzheimer's-associated protein sorLA

The sorting receptor sorLA encoded by the SORL1 gene is implicated in Alzheimers disease (AD) pathogenesis. Genetic studies have identified AD-associated SORL1 mutations and the expression of sorLA in AD brains is reported to be reduced. SorLA is a receptor of the retromer trafficking complex and functions at the endosome, and deficiency in sorLA phenocopies the endosomal pathologies found in AD. SorLA undergoes posttranslational modifications and maturation with ultimate ectodomain shedding, however knowledge of these processes remains limited. Here we demonstrate that sorLA exists at the cell membrane in two forms, an immature and a mature form, characterized by distinct N-glycosylation profiles. The mature sorLA form has acquired complex type N-glycans and is shed from the cell surface by the TACE juxtmembrane cleavage. The immature form of sorLA present at the cell surface is shown to have immature ER-type N-glycans (high-mannose type susceptible to endo H) and does not undergo shedding, however, upon endocytosis and recycling to the cell surface via endosomal trafficking pathways the immature sorLA form acquires complex-type N-glycans. These results suggest an unusual secretion model for sorLA whereby that immature sorLA first traffics to the cell membrane without acquiring Golgi processing of N-glycans, and only upon retrograde trafficking does sorLA acquire normal Golgi maturation of N-glycans and become susceptible to TACE regulated shedding. Supportive evidence for this model include a sorLA mutant with deficient endosomal trafficking and in vivo studies demonstrating requirement of retromer for sorLA trafficking in the brain of retromer VPS26 deficient mice. Collectively, our study establishes the role endosomal trafficking plays in sorLAs normal maturation, and point to impaired maturation as a signature of AD-associated sorLA dysfunction.

cell biology↗

bioRxiv2019

Retromer repletion with AAV9-VPS35 restores endosomal function in the mouse hippocampus

Retromer has emerged as a master conductor of endosomal trafficking, and VPS35 and other retromer-related proteins are found to be deficient in late-onset Alzheimers disease (AD). Depleting VPS35 in neurons impairs retromer function, affecting for example the trafficking of the amyloid-precursor protein (APP) and the glutamate receptor GluA1. Whether VPS35 repletion, after chronic in vivo depletion, can rescue these impairments remains unknown. Here we set out to address this question by using a viral vector approach for VPS35 repletion. First, we completed a series of studies using neuronal cultures in order to optimize AAV9-VPS35 delivery, and to understand how exogenous VPS35 expression affects its endogenous levels as well as its binding to other retromer proteins. Next, we completed a series of studies in wildtype mice to determine the optimum protocol for in vivo delivery of AAV9-VPS35 to the hippocampus. We relied on this information to deliver AAV9-VPS35 to the hippocampus of mice genetically engineered to have chronic, neuronal-selective, VPS35 depletion. VPS35 repletion in the hippocampus was found to normalize APP cleavage and to restore glutamate receptor levels. Unexpectedly, chronic VPS35 depletion in neurons caused glial activation, similar to the pattern observed in AD, which was also partially normalized by VPS35 repletion. Taken together, these studies strengthen the mechanistic link between retromer and AD, and have therapeutic implications.

neuroscience↗

bioRxiv2019

The RhoGEF Cysts couples apical polarity proteins to Rho and myosin activity at adherens junctions

The spatio-temporal regulation of small Rho GTPases is crucial for the dynamic stability of epithelial tissues. However, how RhoGTPase activity is controlled during development remains largely unknown. To explore the regulation of Rho GTPases in vivo we analyzed the Rho GTPase guanine nucleotide exchange factor (RhoGEF) Cysts, the Drosophila orthologue of mammalian p114RhoGEF, GEF-H1, p190RhoGEF, and AKAP-13. Loss of Cysts causes a phenotype that closely resemble the mutant phenotype of the apical polarity regulator Crumbs. This phenotype can be suppressed by the loss of basolateral polarity proteins suggesting that Cysts in an integral component of the apical polarity protein network. Cysts activates Rho at adherens junctions to promote junctional enrichment of myosin II, which requires the RhoGEF domain and the coiled-coil domain containing C-terminal region of Cysts. Cysts recruitment to the apico-lateral cortex depends on Crumbs and Bazooka/Par3 and requires multiple domains within Cysts including the C-terminal region. Together, our findings indicate that Cysts links apical polarity proteins to Rho1 and myosin activation at adherens junctions to support junctional and epithelial integrity in the Drosophila ectoderm.

cell biology↗