Dynein Heavy Chain 64C Differentially Regulates Cell Survival and Proliferation of Wingless-Producing Cells in Drosophila melanogaster

Dynein is a multi-subunit motor protein that moves toward the minus-end of microtubules, and plays important roles in fly development. We identified Dhc64Cm115, a new mutant allele of the fly Dynein heavy chain 64C (Dhc64C) gene whose heterozygotes survive against lethality induced by overexpression of Sol narae (Sona). Sona is a secreted metalloprotease that positively regulates Wingless (Wg) signaling, and promotes cell survival and proliferation. Knockdown of Dhc64C in fly wings induced extensive cell death accompanied by widespread and disorganized expression of Wg. The disrupted pattern of the Wg protein was due to cell death of the Wg-producing cells at the DV midline and overproliferation of the Wg-producing cells at the hinge in disorganized ways. Coexpression of Dhc64C RNAi and p35 resulted in no cell death and normal pattern of Wg, demonstrating that cell death is responsible for all phenotypes induced by Dhc64C RNAi expression. The effect of Dhc64C on Wg-producing cells was unique among components of Dynein and other microtubule motors. We propose that Dhc64C differentially regulates survival of Wg-producing cells, which is essential for maintaining normal expression pattern of Wg for wing development.

A Systematic Review of the Biological Effects of Cordycepin

We conducted a systematic review of the literature on the effects of cordycepin on cell survival and proliferation, inflammation, signal transduction and animal models. A total of 1204 publications on cordycepin were found by the cut-off date of 1 February 2021. After application of the exclusion criteria, 791 papers remained. These were read and data on the chosen subjects were extracted. We found 192 papers on the effects of cordycepin on cell survival and proliferation and calculated a median inhibitory concentration (IC50) of 135 µM. Cordycepin consistently repressed cell migration (26 papers) and cellular inflammation (53 papers). Evaluation of 76 papers on signal transduction indicated consistently reduced PI3K/mTOR/AKT and ERK signalling and activation of AMPK. In contrast, the effects of cordycepin on the p38 and Jun kinases were variable, as were the effects on cell cycle arrest (53 papers), suggesting these are cell-specific responses. The examination of 150 animal studies indicated that purified cordycepin has many potential therapeutic effects, including the reduction of tumour growth (37 papers), repression of pain and inflammation (9 papers), protecting brain function (11 papers), improvement of respiratory and cardiac conditions (8 and 19 papers) and amelioration of metabolic disorders (8 papers). Nearly all these data are consistent with cordycepin mediating its therapeutic effects through activating AMPK, inhibiting PI3K/mTOR/AKT and repressing the inflammatory response. We conclude that cordycepin has excellent potential as a lead for drug development, especially for age-related diseases. In addition, we discuss the remaining issues around the mechanism of action, toxicity and biodistribution of cordycepin.

LGR4 and Its Extracellular Domain as Novel Regulators of ß-Cell Survival and Proliferation

Our lab has shown that RANK (Receptor activator of the NF-κB) by interacting with its ligand, RANKL, inhibits ß-cell proliferation and survival; which can be reversed by Osteoprotegerin (OPG). Recently, the G protein-coupled receptor LGR4 (leucine-rich repeat-containing G protein-coupled receptor 4), which binds R-spondin (RSPO), was identified as a novel receptor for RANKL in osteoclast precursor cells. Thus, RANKL can bind two distinct receptors, RANK and LGR4 in osteoclasts, leading to opposite effects on osteoclastogenesis. LGR4 is expressed in rodent and human ß-cells, but the role of this receptor in ß-cells remains unknown. We postulated that LGR4 through its interaction with RANKL is involved in regulating ß-cell survival and proliferation. Our data indicate expression of specific LGR4 family members, Lgr4, Rank, Rankl, is modulated by stressors, such as cytokines, ER stress, diabetes and aging, in INS1 cells, rodent and human islets. Knocking down Lgr4 in INS1 cells or rodent islets has no significant effect on ß-cell proliferation but is detrimental for ß-cell survival in basal and cytokine-stimulated conditions. We also propose that the soluble extracellular domain of LGR4 (LGR4-ECD), which binds to its ligands (RSPO/RANKL), holds therapeutic potential like OPG, by inhibiting the interaction between RANKL/RANK. At 200ng/ml LGR4-ECD significantly enhances young adult (8-12-week-old) and aged (1.y.o.) rodent ß-cell proliferation, as well as human ß-cell proliferation, in islets from not only control subjects (45±17 y.o.), but also with Type 2 diabetes (48±7 y.o.). Additionally, LGR4-ECD significantly promotes mouse and human ß-cell survival against cytokine-induced cell death. Future studies will determine the physiological role of LGR4 and the therapeutic potential of LGR4-ECD on the beta cell in vivo in basal conditions and in the setting of diabetes. Acknowledgements: Funding: JDRF postdoctoral fellowship # 3-PDF-2020-936-A-N to JF; Human Islets: IIDP

Food for thought: How cell adhesion coordinates nutrient sensing

Cell adhesion controls cell survival and proliferation via multiple mechanisms. Rabanal-Ruiz et al. (2021. J. Cell Biol.https://doi.org/10.1083/jcb.202004010) demonstrate that focal adhesions are key signaling hubs for cellular nutrient sensing and signaling.