The sweet smell of success: Conclusive evidence that cyclic AMP hydrolysis does not trigger fast adaptation in olfactory receptor cells

Involvement of Cx43 phosphorylation in 5'-N-ethylcarboxamide-induced migration and proliferation of mouse embryonic stem cells

Despite a lot of gap junction research, the complex connection between gap junction and cell proliferation remains an exciting area of investigation. Thus, we examined the effect of connexin 43 (Cx43) on the migration and proliferation of embryonic stem (ES) cells and its related signaling pathways following stimulation with the adenosine analogue 5'-N-ethylcarboxamide (NECA). NECA increased phosphorylation of Cx43 which was blocked by caffeine, a non-selective adenosine receptor antagonist. In experiment to measure the gap junctional intercellular communication, NECA blocked transfer of Lucifer yellow to neighboring cells in a scrape loading/dye transfer (SL/DT) assay. In addition, NECA-induced phosphorylation of phosphoinositide 3-kinase (PI3K)/Akt, protein kinase C (PKC), mitogen-activated protein kinases (MAPKs), and nuclear factor-kappa B (NF-kappaB) signal pathways. Inhibition of these signaling pathways reduced NECA-induced phosphorylation of Cx43. Moreover, NECA-treated cells demonstrated phosphorylation of Src, which was blocked by caffeine. In this experiment, a disruption of Cx43 using Cx43-specific small interfering RNA (siRNA) also enhanced Src phosphorylation. In a further study, phosphorylations of integrin beta1, focal adhesion kinase (FAK), and paxillin by NECA were restrained by caffeine as well as the Src blocker, PP2. Finally, we identified that NECA-stimulated cell migration and expressions of cell-cycle regulatory proteins [cyclin D1, cyclin-dependent kinase (CDK) 4, cyclin E, and CDK2]; these increases were inhibited by caffeine, or PP2. We conclude that NECA-stimulated Cx43 phosphorylation mediated by PI3K/Akt, PKC, MAPKs, and NF-kappaB, which subsequently stimulated cell migration and proliferation through Src, integrin beta1, FAK, and paxillin signal pathways.

Role of plasma membrane calcium ATPases in calcium clearance from olfactory sensory neurons

Odorants cause Ca(2+) to rise in olfactory sensory neurons (OSNs) first within the ciliary compartment, then in the dendritic knob, and finally in the cell body. Ca(2+) not only excites but also produces negative feedback on the transduction pathway. To relieve this Ca(2+)-dependent adaptation, Ca(2+) must be cleared from the cilia and dendritic knob by mechanisms that are not well understood. This work focuses on the roles of plasma membrane calcium pumps (PMCAs) through the use of inhibitors and mice missing 1 of the 4 PMCA isoforms (PMCA2). We demonstrate a significant contribution of PMCAs in addition to contributions of the Na(+)/Ca(2+) exchanger and endoplasmic reticulum (ER) calcium pump to the rate of calcium clearance after OSN stimulation. PMCAs in neurons can shape the Ca(2+) signal. We discuss the contributions of the specific PMCA isoforms to the shape of the Ca(2+) transient that controls signaling and adaptation in OSNs.