The spatiotemporal relationship between local Ca(2+) signaling and P2X2R-activated membrane blebbing

ATP increases head volume in capacitated human sperm via a purinergic channel

Scanning ion-conductance microscopy allowed us to document an external Ca²⁺ dependent ATP driven volume increase (ATPVI) in capacitated human sperm heads. We examined the involvement of purinergic receptors (PRs) P2X2R and P2X4R in ATPVI using their co-agonists progesterone and Ivermectin (Iver), and Cu²⁺, which co-activates P2X2Rs and inhibits P2X4Rs. Iver enhanced ATPVI and Cu²⁺ and 5BDBD inhibited it, indicating P2X4Rs contributed to this response. Moreover, Cu²⁺ and 5BDBD inhibited the ATP-induced acrosome reaction (AR) which was enhanced by Iver. ATP increased the concentration of intracellular Ca²⁺ ([Ca²⁺]_i) in >45% of individual sperm, most of which underwent AR monitored using FM4-64. Our findings suggest that human sperm P2X4R activation by ATP increases [Ca²⁺]_i mainly due to Ca²⁺ influx which leads to a sperm head volume increase, likely involving acrosomal swelling, and resulting in AR.

Enteric glial cells immunoreactive for P2X7 receptor are affected in the ileum following ischemia and reperfusion

The aim of this study was to analyze the effect of ischemia and reperfusion injury (IS) on enteric glial cells (EGCs) and neurons immunoreactive for the P2X7 receptor. Intestinal ischemia was induced by obstructing blood flow in the ileal vessels for 35 min. Afterwards, the vessels were reperfused for 14 days. Tissues were prepared for immunohistochemical labeling of P2X7 receptor, HuC/D (Hu) (pan-neuronal marker) and S100β (glial marker); HuC/D (Hu) and glial fibrillary acidic protein (GFAP, glial marker)/DAPI (nuclear marker); or S100β and GFAP/DAPI. Qualitative and quantitative analyses of colocalization, density, profile area and cell proliferation were performed via fluorescence and confocal laser scanning microscopy. The quantitative analyses revealed that a) neurons and EGCs were immunoreactive for P2X7 receptor; b) the P2X7 receptor immunoreactive cells and Hu immunoreactive neurons were reduced after 0 h and 14 days of reperfusion; c) the S100β and GFAP immunoreactive EGCs were increased; d) the profile area of S100β immunoreactive EGCs was increased by IS; e) few GFAP immunoreactive proliferated at 14 days of reperfusion; f) distinct populations of glial cells can be discerned: S100β⁺/GFAP⁺ cells, S100β⁺/GFAP^- cells and S100β^-/GFAP ⁺ cells; g) histological analysis revealed less alterations in the epithelium cells in the IS groups and h) myeloperoxidase reaction revealed increased of the neutrophils in the lamina propria in the IS groups. This study showed that IS is associated with significant neuronal loss, increase of glial cells and altered purinergic receptor expression and that these changes may contribute to intestinal disorders.

Autonomous Cell Migration to CSF1 Sources via a Synthetic Protein-Based System

Inflammatory lesions, often seen in diseases such as rheumatoid arthritis, atherosclerosis and cancer, feature an acidic (i.e., low pH) microenvironment rampant with cytokines, such as CSF1. For potential therapeutic intervention targeted at these CSF1 sources, we have assembled a system of four proteins inside a cell (i.e., HEK293) that initially had no natural CSF1-seeking ability. This system included a newly engineered CSF1 chimera receptor (named CSF1Rchi), the previously engineered Ca²⁺ activated RhoA (i.e., CaRQ), vesicular stomatitis virus glycoprotein G (VSVG) and thymidine kinase (TK). The binding of CSF1 to the CSF1Rchi generated a Ca²⁺ signal that activated CaRQ-mediated cellular blebbing, allowing autonomous cell migration toward the CSF1 source. Next, the VSVG protein allowed these engineered cells to fuse with the CSF1 source cells, upon low pH induction. Finally, these cells underwent death postganciclovir treatment, via the TK suicide mechanism. Hence, this protein system could potentially serve as the basis of engineering a cell to target inflammatory lesions in diseases featuring a microenvironment with high levels of CSF1 and low pH.