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Emerging Concepts in Ion Channel Biophysics
Poster Abstracts
82
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.