Emerging Concepts in Ion Channel Biophysics

Emerging Concepts in Ion Channel Biophysics

Poster Abstracts

50-POS Board 50 Modulation of Store-operated Calcium Channels by a Bis-boronate Ester Derived from L- leucine.

María Guadalupe Montiel-Jaen , Teresa Mancilla-Percino, Guillermo Avila. CINVESTAV-IPN, Mexico City, Mexico.

INTRODUCTION: Orai1 is a Ca 2+ channel of the plasma membrane that is activated during a process known as store-operated calcium entry (SOCE). A decrease in the sarcoplasmic reticulum (SR) Ca 2+ content results in oligomerization of an SR protein (STIM), which promotes the formation of a complex between STIM and Orai1 and ultimately activates the Ca 2+ permeability of the latter. Orai1 can be blocked by La 3+ , and it is also well known that this channel is modulated by certain boron compounds (borinates), such as 2-aminoethyl diphenylborinate or 2-APB. OBJECTIVE: Recently, we synthesized a new series of borinates, derived from α-amino acids, and here we decided to investigate whether one of these novel compounds (bis-borinate ester derived from L-leucine) also modulates Orai1. METHODS AND RESULTS: The experimental model was myotubes obtained from the C2C12 cell line, in which we recorded an inward current identical to an I SkCRAC reported previously in mice myotubes (i.e. with similar biophysical and pharmacological properties; Biophys J 103: 202-11). The store was depleted using the combination of a repetitive stimulation protocol and a Ca 2+ chelator (BAPTA, 20 mM). Under whole-cell patch-clamp conditions, it was possible to record an inward Ca 2+ current that was sensitive to both La 3+ (10 µM) and 2-APB (10 and 75 µM). Remarkably, an extracellular application of bis-borinate also modulated this current. More precisely, within 1-2 min of exposure, a relatively fast inhibitory effect was observed, with an IC 50 of 228 nM. This value was approximately 20-fold lower than that observed with 2-APB (4 µM). Thus, this novel compound acted more potently than a classic modulator of Orai1. CONCLUSIONS: The bis- borinates ester derived from α-amino acids represent novel tools that might help to investigate structural and pathophysiological aspects of Orai1.

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