PI3K-alpha translocation mediates nuclear PtdIns(3,4,5)P3 effector signaling in colorectal cancer

Emerging role of mesenchymal cells in cardiac and cerebrovascular diseases: Physiology, pathology, and therapeutic implications

In recent years, the therapeutic utility of mesenchymal stem cells (MSCs) has received substantial attention from investigators, owing to their pleiotropic properties. The emerging insights from the developments in tissue engineering provide perspectives for the repair of damaged tissue and the replacement of failing organs. Perivascular cells including MSC-like pericytes, vascular smooth muscles, and other cells located around blood vessels, have been acknowledged to contribute to in situ angiogenesis and repair process. MSCs offer a wide array of therapeutic applications in different pathological states. However, in the current article, we have highlighted the recent updates on MSCs and their key applications in cardiac and cerebrovascular diseases, evident in different preclinical and clinical studies. We believe the present article would assist the investigators in understanding the recent advances of MSCs and exploring their therapeutic potential in varied ailments, especially cardiac and cerebrovascular diseases.

Maternal exercise prevents metabolic disorders in offspring mice through SERPINA3C

Maternal exercise can improve the metabolic health of the offspring. However, the molecular mechanisms underlying the beneficial effects of maternal exercise on the offspring remain unclear. Here, we show that maternal exercise during pregnancy alleviates high-fat diet (HFD)-induced adipose inflammation and glucose intolerance in offspring mice, accompanied by upregulation of the adipokine serine protease inhibitor A3C (SERPINA3C) both in maternal adipose tissues and the fetal circulation. Adipose SERPINA3C knockdown impairs, but its overexpression in dams mimics, maternal exercise-mediated metabolic benefits in HFD-fed offspring. Maternal SERPINA3C is transported into the fetal circulation and promotes Krüppel-like factor 4 (Klf4) gene promoter demethylation in fetal preadipocytes to increase KLF4 expression, which inhibits adipose inflammation in HFD-fed offspring mice. The SERPINA3C-cathepsin G-integrin β1 axis activates phosphatidylinositol 3-kinase signalling in preadipocytes. This promotes nuclear translocation of the p110β subunit to generate phosphatidylinositol 3,4,5-trisphosphate (PIP3) in the nucleus. O-linked β-N-acetylglucosamine (O-GlcNAc) transferase then binds to PIP3 to promote ten-eleven translocation methylcytosine dioxygenase 1 (TET1) O-GlcNAcylation, thereby enhancing TET1 activity to facilitate Klf4 gene promoter demethylation. These results provide mechanistic insights into maternal exercise-mediated improvement of offspring metabolism.

Cell-Permeable Fluorescent Sensors Enable Rapid Live Cell Visualization of Plasma Membrane and Nuclear PIP3 Pools

Phosphoinositides, phospholipids that are key cell-signal mediators, are present at very low levels in cellular membranes and within nuclei. Phosphatidylinositol-(3,4,5)-trisphosphate (PIP3), a phosphoinositide barely present in resting cell membranes, is produced when cells receive either growth, proliferation, or movement signals. Aberrant PIP3 levels are associated with the formation of cancers. PIP3 pools are also present in the nucleus, specifically in the nucleolus. However, questions related to the organization and function of this lipid in such membraneless intranuclear structures remain unanswered. Therefore, chemical sensors for tracking cellular PIP3 are invaluable not only for timing signal initiation in membranes but also for identifying the organization and function of membraneless nuclear PIP3 pools. Because PIP3 is present in the inner leaflet of cell membranes and in the nucleus, cell-permeable, rapid-response fluorescent sensors would be ideal. We have designed two peptide-based, water-soluble, cell-permeable, ratiometric PIP3 sensors named as MFR-K17H and DAN-NG-H12G. MFR-K17H rapidly entered into the cell cytoplasm, distinctly reporting rapid (<1 min) time scales of growth factor-stimulated PIP3 generation and depletion within cell membranes in living cells. Importantly, MFR-K17H lighted up inherently high levels of PIP3 in triple-negative breast cancer cell membranes, implying future applications in the detection of enhanced PIP3 levels in cancerous cells. On the other hand, DAN-NG-H12G targeted intranuclear PIP3 pools, revealing that within membraneless structures, PIP3 resided in a hydrophobic environment. Together, both probes form a unique orthogonally targeted combination of cell-permeable, ratiometric probes that, unlike previous cell-impermeable protein-based sensors, are easy to apply and provide an unprecedented handle into PIP3-mediated cellular processes.

PI3K signaling through a biochemical systems lens

Following 3 decades of extensive research into PI3K signaling, it is now evidently clear that the underlying network does not equate to a simple ON/OFF switch. This is best illustrated by the multifaceted nature of the many diseases associated with aberrant PI3K signaling, including common cancers, metabolic disease, and rare developmental disorders. However, we are still far from a complete understanding of the fundamental control principles that govern the numerous phenotypic outputs that are elicited by activation of this well-characterized biochemical signaling network, downstream of an equally diverse set of extrinsic inputs. At its core, this is a question on the role of PI3K signaling in cellular information processing and decision making. Here, we review the determinants of accurate encoding and decoding of growth factor signals and discuss outstanding questions in the PI3K signal relay network. We emphasize the importance of quantitative biochemistry, in close integration with advances in single-cell time-resolved signaling measurements and mathematical modeling.