Biology of the Cell最新文献

Over the past decade, significant advancements have been made in understanding the developmental mechanisms involved in human gastrointestinal formation, with organoids emerging as key experimental models. These three-dimensional in vitro cellular structures mimic the organization and functions of various gut regions, providing a powerful tool for research. By replicating critical stages of gut development, we can now direct the differentiation of cells into specific gastrointestinal tissues. In this protocol, we outline how to generate two types of organoids derived from human pluripotent stem cells (hPSCs): human intestinal organoids (HIOs) and human colonic organoids (HCOs). First, we induce definitive endoderm formation to produce these organoids and specify midgut/hindgut tissues. Three-dimensional spheroids form spontaneously, can be collected, embedded in an extracellular matrix, and cultured over time. During this phase, the organoid epithelium develops, supported by a mesenchymal layer that promotes maturation and differentiation. After a month of culture, HIOs and HCOs reach a developmental and maturation stage comparable to that of the human fetal intestine. These organoids can be used to study human gastrointestinal development, model diseases, and test therapeutic agents.

Sestrins are a stress-inducible family of proteins that function in cell survival and nutrient sensing through their regulation of mTORC1. Muscle wasting is associated with cellular stress, but to date, there is limited in vitro research investigating sestrins in skeletal muscle cells. Here we use C2C12 myotubes to understand how sestrin proteins (sestrin 1–3) are regulated by different forms of cellular stress linked to muscle wasting conditions. Furthermore, since sestrin2 is a well-characterised protein but is lowly expressed in muscle tissue in the absence of stress, we also aimed to determine if silencing this protein impacted parameters of muscle growth or nutrient sensing by mTORC1 under basal conditions. Incubating C2C12 myotubes with the endoplasmic reticulum (ER) stress-inducing agent tunicamycin, or a high concentration (1000 µM) of hydrogen peroxide (H₂O₂), increased sestrin2 protein levels with no change in sestrins 1 or 3. This increase was temporally associated with increased ER stress markers Ddit3 mRNA and ATF4 protein levels, and could be blocked by approximately half when myotubes were co-incubated with H₂O₂ and the ER-stress inhibitor 4-Phenylbutyrate. siRNA silencing of sestrin2 blunted the phosphorylation of the mTORC1 effector S6K1, but did not acutely influence protein synthesis or myotube size. Similarly, silencing sestrin2 did not affect mTORC1 signalling in response to nutrient deprivation. These data indicate that sestrin2 is stress-inducible and may play a role in protecting skeletal muscle from ER stress, but is less important in regulating mTORC1 and nutrient sensing in unstressed/basal conditions.

The endolysosomal system is a highly dynamic and versatile network of organelles essential for maintaining cellular and tissue homeostasis. Its functional diversity relies on a high degree of plasticity, driven by tightly regulated membrane remodeling and intracellular trafficking events. In certain specialized cells, this plasticity enables the formation of lysosome-related organelles, like melanosomes in pigment cells, through the repurposing of ubiquitous membrane trafficking machineries. Disruption of these pathways can lead to pathological conditions, including genetic disorders. In this review, we explore how endolysosomal plasticity underlies key adaptive cellular strategies at the cellular and tissue levels. Focusing on melanocytes, which synthesize melanin, and keratinocytes, which receive and store it, we illustrate how trafficking and membrane dynamics events coordinate between these two cell types for skin pigmentation and photoprotection, and how mutations affecting these processes lead to genetic forms of albinism. By using skin pigmentation as a model of cell- and tissue-specific adaptation, this review highlights the broader physiological and pathological implications of endolysosomal membrane morphodynamics.

Cell junction proteins play a pivotal role in regulating key physiological processes, including proliferation and apoptosis. E-cadherin, a crucial component of adherens junctions, is essential for maintaining intestinal epithelial homeostasis by modulating cell adhesion and proliferation. In this study, we explored the function of E-cadherin in the intestinal epithelial cells. Our findings indicate that during colitis, E-cadherin remains associated with the cell membrane in colonocytes. Furthermore, using an in vitro system, we demonstrated that in colonocytes, E-cadherin inhibits cell proliferation and β-catenin signaling while simultaneously activating the PI3K/Akt pathway. These results suggest that E-cadherin may suppress cell proliferation while promoting PI3K/Akt signaling in colonocytes of colitic mice.