Myosin light chain kinase-driven myosin II turnover regulates actin cortex contractility during mitosis

A TLK2-mediated calcium-driven cell death pathway links neuronal degeneration to nuclear envelope disruption

Calcium overload drives neuronal cell death, but its mechanisms remain unclear. Previous studies in Drosophila implicated tousled-like kinase (TLK) in this process. Here, we investigated TLK2, the mammalian homolog, in calcium overload-induced neuronal death. We found that calcium overload enhances TLK2 expression, multimerization, and phosphorylation, increasing its kinase activity. Inhibiting TLK2 via RNA interference or a small-molecule inhibitor reduced neuronal death, while TLK2 overexpression triggered nuclear envelope (NE) rupture, nuclear enlargement, multinucleation, and cell cycle reentry markers. A protein complex involving TLK2, dynein light chain LC8, and myosin IIA was linked to NE disruption. In mouse models of glaucoma, TLK2 contributed to retinal ganglion cell degeneration, connecting calcium overload to neurodegeneration. We propose "CaToptosis" (Calcium-induced Tousled-like kinase-mediated cell death) as a distinct neuronal death pathway.

RhoA-ROCK2 signaling possesses complex pathophysiological functions in cancer progression and shows promising therapeutic potential

The Rho GTPase signaling pathway is responsible for cell-specific processes, including actin cytoskeleton organization, cell motility, cell division, and the transcription of specific genes. The implications of RhoA and the downstream effector ROCK2 in cancer epithelial-mesenchymal transition, migration, invasion, and therapy resistance associated with stem cells highlight the potential of targeting RhoA/ROCK2 signaling in therapy. Tumor relapse can occur due to cancer cells that do not fully respond to adjuvant chemoradiotherapy, targeted therapy, or immunotherapy. Rho signaling-mediated mitotic defects and cytokinesis failure lead to asymmetric cell division, allowing cells to form polyploids to escape cytotoxicity and promote tumor recurrence and metastasis. In this review, we elucidate the significance of RhoA/ROCK2 in the mechanisms of cancer progression and summarize their inhibitors that may improve treatment strategies.

Structure, regulation, and mechanisms of nonmuscle myosin-2

Members of the myosin superfamily of molecular motors are large mechanochemical ATPases that are implicated in an ever-expanding array of cellular functions. This review focuses on mammalian nonmuscle myosin-2 (NM2) paralogs, ubiquitous members of the myosin-2 family of filament-forming motors. Through the conversion of chemical energy into mechanical work, NM2 paralogs remodel and shape cells and tissues. This process is tightly controlled in time and space by numerous synergetic regulation mechanisms to meet cellular demands. We review how recent advances in structural biology together with elegant biophysical and cell biological approaches have contributed to our understanding of the shared and unique mechanisms of NM2 paralogs as they relate to their kinetics, regulation, assembly, and cellular function.