Phosphoglycerol dihydroceramide, a distinctive ceramide produced by Porphyromonas gingivalis, promotes RANKL-induced osteoclastogenesis by acting on non-muscle myosin II-A (Myh9), an osteoclast cell fusion regulatory factor.

Among several virulence factors produced by the periodontal pathogen Porphyromonas gingivalis (Pg), a recently identified novel class of dihydroceramide lipids that contains a long acyl-chain has the potential to play a pathogenic role in periodontitis because of its higher level of tissue penetration compared to other lipid classes produced by Pg. However, the possible impact of Pg ceramides on osteoclastogenesis is largely unknown. In the present study, we report that the phosphoglycerol dihydroceramide (PGDHC) isolated from Pg enhanced osteoclastogenesis in vitro and in vivo. Using RAW264.7 cells, in vitro assays indicated that PGDHC can promote RANKL-induced osteoclastogenesis by generating remarkably larger TRAP+ multinuclear osteoclasts compared to Pg LPS in a TLR2/4-independent manner. According to fluorescent confocal microscopy, co-localization of non-muscle myosin II-A (Myh9) and PGDHC was observed in the cytoplasm of osteoclasts, indicating the membrane-permeability of PGDHC. Loss- and gain-of-function assays using RNAi-based Myh9 gene silencing, as well as overexpression of the Myh9 gene, in RAW264.7 cells showed that interaction of PGDHC with Myh9 enhances RANKL-induced osteoclastogenesis. It was also demonstrated that PGDHC can upregulate the expression of dendritic cell-specific transmembrane protein (DC-STAMP), an important osteoclast fusogen, through signaling that involves Rac1, suggesting that interaction of PGDHC with Myh9 can elicit the cell signal that promotes osteoclast cell fusion. Taken together, our data indicated that PGDHC is a Pg-derived, cell-permeable ceramide that possesses a unique property of promoting osteoclastogenesis via interaction with Myh9 which, in turn, activates a Rac1/DC-STAMP pathway for upregulation of osteoclast cell fusion.

Numb modulates the paracellular permeability of intestinal epithelial cells through regulating apical junctional complex assembly and myosin light chain phosphorylation.

Numb is highly expressed throughout the crypt-villus axis of intestinal mucosa and functions as cell fate determinant and integrator of cell-to-cell adhesion. Increased paracellular permeability of intestinal epithelial cells is associated with the epithelial barrier dysfunction of inflammatory bowel diseases (IBDs). The apical junctional complex (AJC) assembly and myosin light chain (MLC) phosphorylation regulate adherens junctions (AJ) and tight junctions (TJ). We determined whether and how Numb modulate the paracellular permeability of intestinal epithelial cells. Caco-2 intestinal epithelial cells and their Numb-interfered counterparts were used in the study for physiological, morphological and biological analyses. Numb, expressed in intestinal epithelial cells and located at the plasma membrane of Caco-2 cells in a basolateral to apical distribution, increased in the intestinal epithelial cells with the formation of the intestinal epithelial barrier. Numb expression decreased and accumulated in the cytoplasm of intestinal epithelial cells in a DSS-induced colitis mouse model. Numb co-localized with E-cadherin, ZO-1 and Par3 at the plasma membrane and interacted with E-cadherin and Par3. Knockdown of Numb in Caco-2 cells altered the F-actin structure during the Ca(2+) switch assay, enhanced TNFα-/INF-γ-induced intestinal epithelial barrier dysfunction and TJ destruction, and increased the Claudin-2 protein level. Immunofluorescence experiments revealed that NMIIA and F-actin co-localized at the cell surface of Caco-2 cells. Numb knockdown in Caco-2 cells increased F-actin contraction and the abundance of phosphorylated MLC. Numb modulated the intestinal epithelial barrier in a Notch signaling-independent manner. These findings suggest that Numb modulates the paracellular permeability by affecting AJC assembly and MLC phosphorylation.

DT-13 inhibits breast cancer cell migration via non-muscle myosin II-A regulation in tumor microenvironment synchronized adaptations.

BACKGROUND: Tumor metastasis is a terrifying characteristic of cancer. Numerous studies have been conducted to overcome metastasis by targeting tumor microenvironment (TME). However, due to complexity of tumor microenvironment, it remained difficult for accurate targeting. Dwarf-lillytruf tuber monomer-13 (DT-13) possess good potential against TME. OBJECTIVE: As TME is supportive for tumor metastasis, alternatively it is a challenging for therapeutic intervention. In our present study, we explored molecular mechanism through which TME induced cell migration and how DT-13 interferes in this mechanism. METHODS: We used a novel model of co-culture system which is eventually developed in our lab. Tumor cells were co-cultured with hypoxia induced cancer-associated fibroblasts (CAF) or with chemically induced cancer-associated adipocytes (CAA). The effect of hypoxia in conditioned medium for CAF was assessed through expression of α-SMA and HIF by western blotting while oil red staining was done to assess the successful chemical induction for adipocytes (CAA), the effect of TME through conditioned medium on cell migration was analyzed by trans-well cell migration, and cell motility (wound healing) analyses. The expression changes in cellular proteins were assessed through western blotting and immunofluorescent studies. RESULTS AND CONCLUSION: Our results showed that tumor microenvironment has a direct role in promoting breast cancer cell migration by stromal cells; moreover, we found that DT-13 restricts this TME regulated cell migration via targeting stromal cells in vitro. Additionally we also found that DT-13 targets NMII-A for its effect on breast cancer cell migration for the regulation of stromal cells in TME.