Force-induced motions of the PIEZO1 blade probed with fluorimetry.

Mechanical forces are thought to activate mechanosensitive PIEZO channels by changing the conformation of a large transmembrane blade domain. Yet, whether different stimuli induce identical conformational changes in this domain remains unclear. Here, we repurpose a cyclic permuted green fluorescent protein as a conformation-sensitive probe to track local rearrangements along the PIEZO1 blade. Two independent probes, one inserted in an extracellular site distal to the pore and the other in a distant intracellular proximal position, elicit sizable fluorescence signals when the tagged channels activate in response to fluid shear stress of low intensity. Neither cellular indentations nor osmotic swelling of the cell elicit detectable fluorescence signals from either probe, despite the ability of these stimuli to activate the tagged channels. High-intensity flow stimuli are ineffective at eliciting fluorescence signals from either probe. Together, these findings suggest that low-intensity fluid shear stress causes a distinct form of mechanical stress to the cell.

Mechanical and chemical activation of GPR68 probed with a genetically encoded fluorescent reporter.

G-protein-coupled receptor (GPCR) 68 (GPR68, or OGR1) couples extracellular acidifications and mechanical stimuli to G-protein signaling and plays important roles in vascular physiology, neuroplasticity and cancer progression. Inspired by previous GPCR-based reporters, here, we inserted a cyclic permuted fluorescent protein into the third intracellular loop of GPR68 to create a genetically encoded fluorescent reporter of GPR68 activation we call 'iGlow'. iGlow responds to known physiological GPR68 activators such as fluid shear stress and extracellular acidifications. In addition, iGlow responds to Ogerin, a synthetic GPR68-selective agonist, but not to a non-active Ogerin analog, showing the specificity of iGlow-mediated fluorescence signals. Flow-induced iGlow activation is not eliminated by pharmacological modulation of downstream G-protein signaling, disruption of actin filaments or application of GsMTx4, an inhibitor of certain mechanosensitive ion channels activated by membrane stretch. Deletion of the conserved helix 8, proposed to mediate mechanosensitivity in certain GPCRs, does not eliminate flow-induced iGlow activation. iGlow could be useful to investigate the contribution of GPR68-dependent signaling in health and disease.

Combination Therapy of Apremilast and Biologic Agent as a Safe Option of Psoriatic Arthritis and Psoriasis.

INTRODUCTION: Psoriasis is a chronic immune-medicated inflammatory condition that affects 2-3% of the population, which can lead to psoriatic arthritis. There are multiple regimens for the treatment of psoriasis including disease- modifying anti rheumatic drugs (DMARDS) and biologic agent, phototherapy and apremilast. While monotherapy with biologic agents is effective for many patients with psoriasis some patients are not satisfied by the outcome and require combination therapy. No data exist on the safety of apremilast as a component of combination therapy with biological therapies. OBJECTIVE: The aim of the study was to determine the safety of apremilast in combination of biologic therapies in the treatment of plaque psoriasis and psoriatic arthritis. METHODS: This was retrospective study, open label study carried out at a single community Rheumatology center. Twenty-two patients diagnosed with plaque psoriasis and psoriatic arthritis according to American college of Rheumatology criteria-participated. Apremilast was added to their current biologic agent. Patients were permitted to their current biologic treatment. RESULTS: Out of 22 patients, six patients developed side effects, none of which caused discontinuation of therapy. Out of the six patients who developed side effects, two patients developed nausea and two patients developed diarrhea. One patient developed weight loss and one patient developed abdominal pain. CONCLUSION: Apremilast can be safely combined with all biologic agents in patients with plaque psoriasis or psoriatic arthritis not responding adequately to biologics alone.