Pathways of integrins in the endo-lysosomal system

Extracellular matrix ligands modulate the endothelial progenitor cell secretome for enhanced angiogenesis

Wound healing is a complex physiological process fundamentally dependent on angiogenesis for effective tissue repair. Endothelial progenitor cells (EPCs) have shown significant potential in promoting angiogenesis, primarily through their secretome, rich in proteins and extracellular vesicles (EVs) essential for cell signaling and tissue regeneration. This study investigates the effect of a collagen-bound proteoglycan mimetic (LXW7-DS-SILY or LDS), that binds to the αvβ3 integrin receptor, on the EPC secretome, with a dual focus on the proteomic content and the functional properties of EVs. Utilizing high-resolution two-dimensional liquid chromatography-tandem mass spectrometry (LC-MS/MS) alongside bioinformatic analysis, we identified significant alterations in protein expression profiles, particularly in angiogenesis and wound healing pathways. The functional impact of these changes was validated through biological assays, where the whole secretome and the EV fraction from EPCs seeded on collagen-bound LDS markedly enhanced vascular network formation, driven by the increase of growth factors and angiogenic regulators such as FGFR1, NRP1, and ANGPT2 within the EV fraction. Gene Ontology (GO) enrichment analysis further highlighted the enrichment of proteins within the EVs driving biological processes, including 'response to wounding' and 'positive regulation of cell motility'. These results underscore that LDS modulates the EPC secretome and significantly enhances its angiogenic potential, offering a promising therapeutic strategy for non-healing and ischemic wounds and suggesting that biomaterials can be modified to control the EV secretome to enhance tissue repair. Functional assays validating the omics data highlight the robustness of LDS as a targeted therapeutic for enhancing angiogenesis and tissue repair in clinical settings. Moreover, the pivotal role of EVs in mediating pro-angiogenic effects offers insights into developing biomaterial therapies that exploit key regulators within the EPC secretome for wound healing. STATEMENT OF SIGNIFICANCE: This manuscript explores how a proteoglycan mimetic that binds to both collagen and the αvβ3 integrin receptor affects the proteome component of the secretome from endothelial progenitor cells (EPCs). It presents functional biological data, analytical data, and proteomic analysis of the soluble and extracellular vesical (EV) components of the secratome. The proteomic data maps to the observed enhanced angiogenic potential of the EVs. These results suggest that by controlling the cellular environment and judicially engineering how cells interact with a biomaterial can influence the proteomic composition of EVs to enhance tissue regeneration. This is the foundation of future work aimed at engineering biomaterial cell systems to influence the proteomic component of EVs for therapeutic use.

Response of epithelial cell lines from the rainbow trout gut and gill to ammonia

Rainbow trout epithelial cell lines from the gill, RTgill-W1, and gut, RTgutGC, were exposed to NH4Cl at 18-21 °C in L15 (basal medium) with fetal bovine serum and were found to undergo cytoplasmic vacuolization and cell death, depending on NH4Cl concentration and exposure time. Vacuolization arose within 24 h of cultures being exposed to 10-100 mM NH4Cl, and vacuoles disappeared over 24 h after NH4Cl-exposed cultures were returned to just L15/FBS. RTgill-W1 appeared more sensitive to vacuolization, with one indicator being the maximal proportion of vacuolated cells in a culture, which approached 100% in 50 mM NH4Cl for 72 h. RTgill-W1 also were more sensitive to NH4Cl-induced cell killing. For 7-d exposures, the inhibitory concentrations (IC50s) for the 50% loss of cell viability as evaluated with Alamar Blue were 30 mM NH4Cl for RTgill-W1 and 80 mM for RTgutGC. In a wound-healing assay, RTgutGC cells in 0.1 and 1 mM NH4Cl were able to migrate and cover a 500-μm gap in 5 d, like the control, but in 50 mM NH4Cl healing was blocked. In 10 mM NH4Cl, repair was slowed but by 14 d the gap was covered with cells and many of these were vacuolated. Overall, the results provide a foundation for using these two cell lines to study the physiology and toxicology of ammonia in fish.

The IP3R inhibitor desmethylxestospongin B reduces tumor cell migration, invasion and metastasis by impairing lysosome acidification and β1-integrin recycling

Cancer is the second leading cause of death worldwide. >90 % of cancer-related deaths are due to metastasis, a process that depends on the ability of cancer cells to leave the primary tumor, migrate, and colonize different tissues. Inositol 1,4,5-trisphosphate receptor (IP3R)-mediated Ca2+ signaling plays an essential role in maintaining the homeostasis of cancer cells and the sustained proliferation. Desmethylxestospongin B (dmXeB) is a specific inhibitor of the IP3R that selectively arrests cell proliferation and promotes cancer cell death at high concentrations. However, whether migration, invasion and metastasis can be affected by this drug is unknown. Here, by using the highly metastatic triple negative breast cancer (TNBC) cell line MDA-MB-231, we demonstrate that a prolonged inhibition of IP3R-mediated Ca2+ signals with dmXeB significantly reduces cell migration and invasion in vitro and metastasis in vivo. We found that this phenomenon was independent of the bioenergetic control of IP3R over the mitochondria and AMPK activation. Furthermore, employing a tandem LC3-GFP-mcherry assay, we found that prolonged inhibition of IP3R with dmXeB leads to diminished autophagic flux. This reduction can be attributed to impaired lysosomal acidification, as evidenced by assessments using DQ-BSA and pHrodo. Since cell migration requires appropriate assembly and disassembly of focal adhesions, along with the internalization and recycling of integrins via autophagy, we explored the dependency of integrin recycling from autophagosomes, finding that IP3R inhibition with dmXeB impaired the recycling of β1-integrins, which accumulated within autophagosomes. Our findings reveal an unexpected effect of IP3R inhibition with dmXeB in cancer cells that could represent a novel therapeutic strategy for the treatment of cancer metastasis.

Deletion of Tmem268 in mice suppresses anti-infectious immune responses by downregulating CD11b signaling

Transmembrane protein 268 (TMEM268) is a novel, tumor growth-related protein first reported by our laboratory. It interacts with the integrin subunit β4 (ITGB4) and plays a positive role in the regulation of the ITGB4/PLEC signaling pathway. Here, we investigated the effects and mechanism of TMEM268 in anti-infectious immune response in mice. Tmem268 knockout in mice aggravated cecal ligation and puncture-induced sepsis, as evidenced by higher bacterial burden in various tissues and organs, congestion, and apoptosis. Moreover, Tmem268 deficiency in mice inhibited phagocyte adhesion and migration, thus decreasing phagocyte infiltration at the site of infection and complement-dependent phagocytosis. Further findings indicated that TMEM268 interacts with CD11b and inhibits its degradation via the endosome-lysosome pathway. Our results reveal a positive regulatory role of TMEM268 in β2 integrin-associated anti-infectious immune responses and signify the potential value of targeting the TMEM268-CD11b signaling axis for the maintenance of immune homeostasis and immunotherapy for sepsis and related immune disorders.

Neuronal Autophagy: Regulations and Implications in Health and Disease

Autophagy is a major degradative pathway that plays a key role in sustaining cell homeostasis, integrity, and physiological functions. Macroautophagy, which ensures the clearance of cytoplasmic components engulfed in a double-membrane autophagosome that fuses with lysosomes, is orchestrated by a complex cascade of events. Autophagy has a particularly strong impact on the nervous system, and mutations in core components cause numerous neurological diseases. We first review the regulation of autophagy, from autophagosome biogenesis to lysosomal degradation and associated neurodevelopmental/neurodegenerative disorders. We then describe how this process is specifically regulated in the axon and in the somatodendritic compartment and how it is altered in diseases. In particular, we present the neuronal specificities of autophagy, with the spatial control of autophagosome biogenesis, the close relationship of maturation with axonal transport, and the regulation by synaptic activity. Finally, we discuss the physiological functions of autophagy in the nervous system, during development and in adulthood.

Paracoccidioides brasiliensis Induces α3 Integrin Lysosomal Degradation in Lung Epithelial Cells

Studies on the pathogen-host interaction are crucial for the understanding of the mechanisms involved in the establishment, maintenance, and spread of infection. In recent years, our research group has observed that the P. brasiliensis species interact with integrin family receptors and increase the expression of α3 integrin in lung epithelial cells within 5 h of infection. Interestingly, α3 integrin levels were reduced by approximately 99% after 24 h of infection with P. brasiliensis compared to non-infected cells. In this work, we show that, during infection with this fungus, α3 integrin is increased in the late endosomes of A549 lung epithelial cells. We also observed that the inhibitor of the lysosomal activity bafilomycin A1 was able to inhibit the decrease in α3 integrin levels. In addition, the silencing of the charged multivesicular body protein 3 (CHMP3) inhibited the reduction in α3 integrin levels induced by P. brasiliensis in A549 cells. Thus, together, these results indicate that this fungus induces the degradation of α3 integrin in A549 lung epithelial cells by hijacking the host cell endolysosomal pathway.

Biochemical Pathways of Cellular Mechanosensing/Mechanotransduction and Their Role in Neurodegenerative Diseases Pathogenesis

In this review, we shed light on recent advances regarding the characterization of biochemical pathways of cellular mechanosensing and mechanotransduction with particular attention to their role in neurodegenerative disease pathogenesis. While the mechanistic components of these pathways are mostly uncovered today, the crosstalk between mechanical forces and soluble intracellular signaling is still not fully elucidated. Here, we recapitulate the general concepts of mechanobiology and the mechanisms that govern the mechanosensing and mechanotransduction processes, and we examine the crosstalk between mechanical stimuli and intracellular biochemical response, highlighting their effect on cellular organelles' homeostasis and dysfunction. In particular, we discuss the current knowledge about the translation of mechanosignaling into biochemical signaling, focusing on those diseases that encompass metabolic accumulation of mutant proteins and have as primary characteristics the formation of pathological intracellular aggregates, such as Alzheimer's Disease, Huntington's Disease, Amyotrophic Lateral Sclerosis and Parkinson's Disease. Overall, recent findings elucidate how mechanosensing and mechanotransduction pathways may be crucial to understand the pathogenic mechanisms underlying neurodegenerative diseases and emphasize the importance of these pathways for identifying potential therapeutic targets.