
==== Front
Res Sq
ResearchSquare
Research Square
2693-5015
American Journal Experts

10.21203/rs.3.rs-4980372/v1
10.21203/rs.3.rs-4980372
preprint
1
Article
Resting human trabecular meshwork cells experience tonic cation influx
Yarishkin Oleg
Lakk Monika
Rudzitis Christopher N.
Kirdajova Denisa
Krizaj David https://orcid.org/0000-0003-4468-3029

28 8 2024
rs.3.rs-4980372https://creativecommons.org/licenses/by/4.0/ This work is licensed under a Creative Commons Attribution 4.0 International License, which allows reusers to distribute, remix, adapt, and build upon the material in any medium or format, so long as attribution is given to the creator. The license allows for commercial use.
https://www.researchsquare.com/article/rs-4980372/v1
nihpp-rs4980372v1.pdf
Abstract

The trabecular meshwork (TM) regulates intraocular pressure (IOP) by converting biochemical and biomechanical stimuli into intracellular signals. Recent electrophysiological studies demonstrated that this process is mediated by pressure sensing ion channels in the TM plasma membrane while the molecular and functional properties of channels that underpin ionic homeostasis in resting cells remain largely unknown. Here, we demonstrate that the TM resting potential is subserved by a powerful cationic conductance that disappears following Na + removal and substitution with choline or NMDG + . Its insensitivity to TTX, verapamil, phenamil methanesulfonate and amiloride indicates it does not involve voltage-operated Na + , Ca 2+ and epithelial Na + (ENaC) channels or Na + /H + exchange while a modest hyperpolarization induced by SEA-0440 indicates residual contribution from reversed Na + /Ca 2+ exchange. Tonic cationic influx was inhibited by Gd 3+ and Ruthenium Red but not GsMTx4, indicating involvement of TRP-like but not Piezo channels. Transcriptional analysis detected expression of most TRP genes, with the canonical transcriptome pool dominated by TRPC1 followed by the expression of TRPV1, TRPC3 and TRPC5. TRPC3 antagonist Pyr3 and TRPC1,4,5 antagonist Pico1,4,5 did not affect the standing current, whereas the TRPC blocker SKF96365 promoted rather than suppressed, Na + influx. TM cells thus maintain the resting membrane potential, control Na + homeostasis, and balance K + efflux through a novel constitutive monovalent cation leak current with properties not unlike those of TRP channels. Yet to be identified at the molecular level, this novel channel sets the homeostatic steady-state and controls the magnitude of pressure-induced transmembrane signals.
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