The Transient Receptor Potential Vanilloid 1 (TRPV1) ion channel is expressed in nociceptors where, when activated by chemical or thermal stimuli, it functions as an important transducer of painful and itch-related stimuli. Although the interaction of TRPV1 with proteins that regulate its function has been previously explored, their modulation by chaperones has not been elucidated, as is the case for other mammalian TRP channels. Here we show that TRPV1 physically interacts with the Sigma 1 Receptor (Sig-1R), a chaperone that binds progesterone, an antagonist of Sig-1R and an important neurosteroid associated to the modulation of pain. Antagonism of Sig-1R by progesterone results in the down-regulation of TRPV1 expression in the plasma membrane of sensory neurons and, consequently, a decrease in capsaicin-induced nociceptive responses. This is observed both in males treated with a synthetic antagonist of Sig-1R and in pregnant females where progesterone levels are elevated. This constitutes a previously undescribed mechanism by which TRPV1-dependent nociception and pain can be regulated.

The transient receptor potential vanilloid 1 (TRPV1) ion channel is mainly found in primary nociceptive afferents whose activity has been linked to pathophysiological conditions including pain, itch and inflammation. Consequently, it is important to identify naturally occurring antagonists of this channel. Here we show that a naturally occurring monounsaturated fatty acid, oleic acid, inhibits TRPV1 activity, and also pain and itch responses in mice by interacting with the vanilloid (capsaicin)-binding pocket and promoting the stabilization of a closed state conformation. Moreover, we report an itch-inducing molecule, cyclic phosphatidic acid, that activates TRPV1 and whose pruritic activity, as well as that of histamine, occurs through the activation of this ion channel. These findings provide insights into the molecular basis of oleic acid inhibition of TRPV1 and also into a way of reducing the pathophysiological effects resulting from its activation.

Background: De novo mutations in calmodulin genes have been recently associated with markedly prolonged QT interval and life-threatening ventricular arrhythmias in infants. Biochemical evidences suggested impaired calcium ion binding to mutant calmodulins. Calcium dependent inactivation (CDI) of L-type calcium channel (ICaL) involves the interaction between Ca 2þcalmodulin and the channel protein. Aims: To explore the effects of two CALM1 mutations (F142L and D130G) on electrical activity and ICaL properties in human induced-pluripotent stem cells (iPSC)-derived cardiomyocytes (CM). Methods: Skin fibroblasts of two patients carrying the mutation CALM1-F142L or CALM1-D130G were reprogrammed to generate iPSC and these cells differentiated into CM; a healthy donor was selected as control. Two cell clones for each mutation were analyzed to rule out clone specificity. Patch clamp and micro electrode arrays (MEA) analyses were performed on isolated iPSC-derived CM and beating clusters at about 40 days of differentiation respectively. ICaL was isolated in the presence of calcium or barium ions as charge carriers. Results: CALM1-F142L iPSC-derived CM showed prolonged field potential duration (FPD) with high betaadrenergic sensitivity; peak ICaL density was unaltered, but CDI was markedly reduced and inactivation incomplete. CALM1-D130G iPSC-derived CM showed higher ICaL density and unaltered CDI. Conclusions: F142L and D130G calmodulin mutations differently affect ICaL properties in human iPSC-derived CM. F142L mutation is consistent with reduced calcium affinity of calmodulin; D130G abnormality suggests ICaL facilitation instead, possibly resulting from upregulation of alternative calmodulin isoforms. Overall, both calmodulin mutations might potentially cause arrhythmogenic calcium overload. 1687-Pos Board B417Aging Increases Cardiac L-Type Calcium Channel Current of Ventricular Myocytes from Male Hearts via a PKA-Dependent Mechanism Sylvain Brunet. Neurosciences, Cleveland Clinic Foundation, Cleveland, OH, USA. Consistent findings of the aging heart include diastolic dysfunctions and attenuated b-adrenergic receptor (b-AR) stimulation of heart rate and contractility. However, variable results were reported for the impact of aging on L-type Ca channel (LTCC) function, the trigger of excitation-contraction. In this study, we evaluated the impact of aging and gender on LTCC of ventricular myocytes (VM). VMs were isolated from LV of young and old mice (C57BL/6) hearts of both gender and processed for whole-cell voltage clamp recording to measure LTCC current. VMs from old male showed increased LTCC current density compared to young VMs. LTCC peak current density were À5.7 5 0.3 pA/pF (n=33) and À12.6 5 1.7 pA/pF (n ¼ 21) (P < 0.01), for young and old, respectively. Application of PKI, a selective PKA inhibitor, reseted LTCC current density of old VMs to levels comparable to young VMs. PKI application decreased LTCC peak current density by 1557% and 5955% (P < 0.05) in young and old VMs, respectively. Lastly, we tested the ...