TRANSIENT RECEPTOR POTENTIAL V1 REGULATES ACTIVATION AND MODULATION OF TRANSIENT RECEPTOR POTENTIAL A1 BY Ca2+

The transient receptor potential A1 (TRPA1) channel contributes to nociceptive signaling in certain pain models It has been suggested that Ca2+, which activates and modulates TRPA1, could play a critical regulatory role in this process Since TRPA1 and transient receptor potential V1 (TRPV1) channels are co-expressed and interact in neurons, we investigated whether activation and modulation of TRPA1 by Ca2+ is regulated by TRPV1 Cell-attached recordings showed that TRPA1 is activated by extracellular Ca2+ ([Ca2+](e)) in concentration response fashion This activation, especially by 2 mM [Ca2+](e) was substantially suppressed by co expression with TRPV1 Inside-out recordings demonstrated that intracellular Ca2+ ([Ca2+](i)) triggered activation of TRPA1 was attenuated by the presence of TRPV1 only at 2 mM [Ca2+]e, but not in Ca2+-free conditions Further depletion of internal Ca2+ stores by thapsigargin generated TRPA1-mediated currents, which is affected by TRPV1 in both Chinese hamster ovary cells and sensory neurons Since mustard oil current (I-MO) is modulated by [Ca2+](e) we next examined whether alterations in the Ca2+-permeability of TRPV1 by mutating Y671 effect I-MO properties First it was demonstrated that the mutations in TRPV1 did not affect association of the TRPA1 and TRPV1 channels However, these TRPV1 mutations, particularly Y671K, altered the following characteristics of TRPA1 magnitude of I-MO in presence and absence of [Ca2+](e), the influence of [Ca2+](e) on the voltage dependency of I-MO, and open probability of single-channel I-MO In summary, activation of TRPA1 by [Ca2+](e) and [Ca2+](i) is controlled by the TRPV1 channel, and characteristics of I-MO depend on Ca2+ permeability of the TRPV1 channel (C) 2010 IBRO Published by Elsevier Ltd All rights reserved