THY1-mediated mechanisms converge to drive YAP activation in skin homeostasis and repair.

Anchored cells of the basal epidermis constantly undergo proliferation in an overcrowded environment. An important regulator of epidermal proliferation is YAP, which can be controlled by both cell-matrix and cell-cell interactions. Here, we report that THY1, a GPI-anchored protein, inhibits epidermal YAP activity through converging molecular mechanisms. THY1 deficiency leads to increased adhesion by activating the integrin-ß1-SRC module. Notably, regardless of high cellular densities, the absence of THY1 leads to the dissociation of an adherens junction complex that enables the release and translocation of YAP. Due to increased YAP-dependent proliferation, Thy1-/- mice display enhanced wound repair and hair follicle regeneration. Taken together, our work reveals THY1 as a crucial regulator of cell-matrix and cell-cell interactions that controls YAP activity in skin homeostasis and regeneration.

Do Different Stemness Markers Identify Different Pools of Cancer Stem Cells in Malignancies: A Study on ER+ and ER-Breast Cancer Cell Lines.

In view of popularity of cancer stem cell (CSC) model all events in evolution of cancer are being explained in that context. Breast cancer is first solid tumor in which CSCs were identified. We aimed to compare stemness profile of two major subtypes [Estrogen receptor positive (ER+) and negative (ER-)] breast cancer using different sets of markers. Expression of CD44/CD24, CK/Vimentin, E-Cadherin/Fibronectin and percentage of side population (SP) was studied in ER+ (T47D) and ER- (MDA-MB-231) cell lines by flow cytometry. Breast CSCs (BCSCs) were sorted using CD44+/CD24-/low expression and SP analysis and cultured. BCSCs were then compared with Non-CSCs (NCSCs) for response to drugs (Paclitaxel and Cisplatin), Ki67 and ER expression. Results showed higher expression of stemness markers (CD44+/CD24-/low, CK+/Vimentin+ and E-Cadherin-/FibrinectinF+) in MDA-MB-231 cells. Percentage SP representing BCSCs was found to be significantly more in later (3.20 ± 0.002 cf. T47D 1.25% ± 0.0007). BCSCs were found to be more resistant to drugs as compared to NCSCs in both cell lines. ER expression was weak in BCSCs sorted from T47D as compared to NCSCs. Ki67 was expressed in both BCSCs and NCSCs. Differences in expression of stemness markers help to explain aggressive behavior, higher recurrence rate and metastatic potential of MDA-MB-231 cells. However, no correlation amongst different markers used suggests that they may be identifying varied populations of cells in tumor hierarchy. A weak ER expression in BCSCs may be strategy used by BCSCs to escape effect of hormone therapy in ER+ breast cancers.

Identification of a distal allosteric ligand binding pocket in HtrA3.

Human HtrA3 (High temperature requirement protease A3) is a trimeric PDZ bearing propapoptotic serine protease, which is involved in various diseases including cancer and pre-eclampsia. Proposed to be a tumor suppressor, its role as a potential therapeutic target is strongly advocated. Therefore, it becomes imperative to gain insights into its mechanism of action and regulation. Allostery is a well-known mechanism of catalytic activation for many HtrA3 homologs, which opens up avenues for manipulating enzyme functions for therapeutic intervention. In our study, through in silico and biochemical approaches, we have reported for the first time that HtrA3 shows allosteric behaviour. We identified a novel selective binding pocket, which triggers conformational reorientations through signal propagation to the distantly situated active-site pocket via the functionally important loop regions. Using molecular docking, simulation studies and biochemical studies we have identified the regulatory movements at and around the active site pocket. Our study is the first one to report a non-classical binding site for HtrA3, which is instrumental for formation of a catalytically efficient orthosteric pocket upon substrate binding.