Guzman-Hernandez, M. L. | Search bioRxiv

bioRxiv2024

FKBP12-BOUND CALCINEURIN CONTROL TMEM16A ACTIVITY

The Ca2+-dependent Cl- channel TMEM16A activity is vital for mammals. Critical functions such as blood pressure, pain, fluid and electrolyte secretion, peristalsis, and electrical activity depend on TMEM16A Cl- fluxes. Ciclosporin A (CsA) and FK506, two immunosuppressants that inhibit calcineurin (CaN), down-regulate TMEM16A function. However, the underlying mechanism remains undetermined. CsA binds to cyclophilin 1, whereas FK506 binds to FKBP12, and both complexes subsequently inhibit CaN, a phosphatase that maintains TMEM16A function. Here, we show that TMEM16A-EGFP and mRFP-FKBP12 colocalize in HEK-AD293 cells stimulated with the Ca2+ ionophore ionomycin, FKBP12 co-immunoprecipitated with TMEM16A expressed in CaN-depleted HEK-AD293 cells, ionomycin favoured TMEM16A and FKBP12 interaction in a bimolecular fluorescence complementation assay in live cells, and TMEM16A currents recorded from CaN-depleted HEK-AD293 cells were insensitive to CsA and FK506. These data support the idea that FKBP12 works as an auxiliary protein of TMEM16A, thus enabling the interaction of CaN under physiological conditions. This heteromerization is essential to sustain TMEM16A activity. On the contrary, disrupting the Ca2+-stimulated CaN-FKBP12-TMEM16A heterotrimer or inhibiting CaN with CsA or FK506 does not preclude TMEM16A activation but decreases activity.

physiology↗

bioRxiv2021

TRICLOSAN IS A KCNQ3 POTASSIUM CHANNEL ACTIVATOR

KCNQ channels participate in the physiology of several cell types. In neurons of the central nervous system, the primary subunits are KCNQ2, 3 and 5. Activation of these channels silence the neurons, limiting action potential duration and preventing high-frequency action potential burst. Mutation of the KCNQ genes are associated with a wide spectrum of phenotypes characterized by hyperexcitability. Activation of KCNQ channels is an attractive strategy to treat epilepsy and other hyperexcitability conditions as are the evolution of stroke and traumatic brain injury. In this work we show that triclosan, a bactericide widely used in personal care products, activates the KCNQ3 channels but not the KCNQ2. Triclosan induces a voltage shift in the activation, increases the conductance and slows the closing of the channel. The effect is independent of PIP2. The putative binding site is located in the pore region but is distinct from the binding site for retigabine. Our results indicate that triclosan is a new activator for KCNQ channels.

biophysics↗