Cholesterol and Sphingomyelin Polarize at the Leading Edge of Migrating Myoblasts and Involve Their Clustering in Submicrometric Domains

Enhanced Natural Killer Cell Proliferation by Stress-Induced Feeder Cells

Natural killer (NK) cells, integral to the innate immune system, are notable in cell therapies because of their applicability in allogeneic treatments, distinguishing them from T cells typically employed in conventional cell therapies. However, their limited half-life (proliferative capability) poses a challenge for therapy. The limited half-life creates difficulties in obtaining a sufficient number of cells for in vitro adoptive therapy. Gene modification is commonly employed to address this limitation. However, due to concerns such as genetic instability and unintended gene expression, its suitability for long-term cultivation is uncertain. Consequently, safer alternatives are needed. We aimed to promote NK cell proliferation through feeder cells rather than genetic modification. These cells are designed to interact with NK cells without adverse effects, aiming to promote NK cell proliferation more safely. In our study, during the tailoring of feeder cells, we excluded genetic modification and instead applied chemical-based extracellular stress. The extracellular stress applied consisted of hypoxia and cytochalasin D. By treating the feeder cells with these stressors, we were able to inhibit feeder cell proliferation, enabling them to function more efficiently as feeder cells. Furthermore, we observed that the feeder cells subjected to extracellular stress exhibited upregulated expression of 4-1BBL, which enhances the 4-1BB/4-1BBL interaction with NK cells. The upregulated 4-1BBL binds to 4-1BB on the surface of NK cells, promoting their proliferation. Additionally, following coculture with feeder cells exposed to extracellular stress, we observed an upregulation of CD56 expression on the surface of NK cells. These CD56bright NK cells influence NK cell proliferation through enhanced cytokine release. We further validated this process under dynamic conditions where shear stress is applied, demonstrating that the feeder cell-mediated enhancement of NK cell proliferation is applicable under dynamic conditions such as those found in bioreactors.

Bioactive sphingolipids as emerging targets for signal transduction in cancer development

Sphingolipids, crucial components of cellular membranes, play a vital role in maintaining cellular structure and signaling integrity. Disruptions in sphingolipid metabolism are increasingly implicated in cancer development. Key bioactive sphingolipids, such as ceramides, sphingosine-1-phosphate (S1P), ceramide-1-phosphate (C1P), and glycosphingolipids, profoundly impact tumor biology. They influence the behavior of tumor cells, stromal cells, and immune cells, affecting tumor aggressiveness, angiogenesis, immune modulation, and extracellular matrix remodeling. Furthermore, abnormal expression of sphingolipids and their metabolizing enzymes modulates the secretion of tumor-derived extracellular vesicles (TDEs), which are key players in creating an immunosuppressive tumor microenvironment, remodeling the extracellular matrix, and facilitating oncogenic signaling within in situ tumors and distant pre-metastatic niches (PMNs). Understanding the role of sphingolipids in the biogenesis of tumor-derived extracellular vesicles (TDEs) and their bioactive contents can pave the way for new biomarkers in cancer diagnosis and prognosis, ultimately enhancing comprehensive tumor treatment strategies.

Piezo1 Regulation Involves Lipid Domains and the Cytoskeleton and Is Favored by the Stomatocyte-Discocyte-Echinocyte Transformation

Piezo1 is a mechanosensitive ion channel required for various biological processes, but its regulation remains poorly understood. Here, we used erythrocytes to address this question since they display Piezo1 clusters, a strong and dynamic cytoskeleton and three types of submicrometric lipid domains, respectively enriched in cholesterol, GM1 ganglioside/cholesterol and sphingomyelin/cholesterol. We revealed that Piezo1 clusters were present in both the rim and the dimple erythrocyte regions. Upon Piezo1 chemical activation by Yoda1, the Piezo1 cluster proportion mainly increased in the dimple area. This increase was accompanied by Ca2+ influx and a rise in echinocytes, in GM1/cholesterol-enriched domains in the dimple and in cholesterol-enriched domains in the rim. Conversely, the effects of Piezo1 activation were abrogated upon membrane cholesterol depletion. Furthermore, upon Piezo1-independent Ca2+ influx, the above changes were not observed. In healthy donors with a high echinocyte proportion, Ca2+ influx, lipid domains and Piezo1 fluorescence were high even at resting state, whereas the cytoskeleton membrane occupancy was lower. Accordingly, upon decreases in cytoskeleton membrane occupancy and stiffness in erythrocytes from patients with hereditary spherocytosis, Piezo1 fluorescence was increased. Altogether, we showed that Piezo1 was differentially controlled by lipid domains and the cytoskeleton and was favored by the stomatocyte-discocyte-echinocyte transformation.

Piezo1 Is Required for Myoblast Migration and Involves Polarized Clustering in Association with Cholesterol and GM1 Ganglioside

A specific plasma membrane distribution of the mechanosensitive ion channel Piezo1 is required for cell migration, but the mechanism remains elusive. Here, we addressed this question using WT and Piezo1-silenced C2C12 mouse myoblasts and WT and Piezo1-KO human kidney HEK293T cells. We showed that cell migration in a cell-free area and through a porous membrane decreased upon Piezo1 silencing or deletion, but increased upon Piezo1 activation by Yoda1, whereas migration towards a chemoattractant gradient was reduced by Yoda1. Piezo1 organized into clusters, which were preferentially enriched at the front. This polarization was stimulated by Yoda1, accompanied by Ca2+ polarization, and abrogated by partial cholesterol depletion. Piezo1 clusters partially colocalized with cholesterol- and GM1 ganglioside-enriched domains, the proportion of which was increased by Yoda1. Mechanistically, Piezo1 activation induced a differential mobile fraction of GM1 associated with domains and the bulk membrane. Conversely, cholesterol depletion abrogated the differential mobile fraction of Piezo1 associated with clusters and the bulk membrane. In conclusion, we revealed, for the first time, the differential implication of Piezo1 depending on the migration mode and the interplay between GM1/cholesterol-enriched domains at the front during migration in a cell-free area. These domains could provide the optimal biophysical properties for Piezo1 activity and/or spatial dissociation from the PMCA calcium efflux pump.