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Emerging Concepts in Ion Channel Biophysics
Poster Abstracts
46
22-POS
Board 22
The Calcium-activated Chloride Channel TMEM16A is Regulated by Cholesterol,
Phosphatidylinositol 4,5-Bisphosphate (PIP2), and Poly-Unsaturated Fatty Acids
José De Jesús-Pérez
1
, Silvia Cruz-Rangel
1
, Edith Espino-Saldaña
2
, Ataúlfo Martínez-Torres
2
,
Criss Hartzell
3
, Patricia Pérez-Cornejo
4
, Jorge Arreola
1
.
1
Universidad Autónoma de San Luis Potosí, San Luis Potosí, San Luis Potosí, Mexico,
2
Instituto
de Neurobiología UNAM, Querétaro, Querétaro, Mexico,
3
Emory University School of
Medicine, Atlanta, GA, USA,
4
Universidad Autónoma de San Luis Potosí School of Medicine,
San Luis Potosí, San Luis Potosí, Mexico.
Fluid secretion of exocrine glands, skeletal and smooth muscle contraction and regulation of
gastrointestinal contraction, are some of the physiological functions that are dependent on the Cl
-
efflux via the homo-dimeric calcium-activated chloride channel TMEM16A. The gating of
TMEM16A results from the interaction between the binding of intracellular Ca
2+
, membrane
depolarization, extracellular proton concentration, and permeant anions. Membrane lipids
regulate proteins activity such as ionic channel. In this work, we study the regulation of
TMEM16A by cholesterol, phosphatidylinositol 4,5-bisphosphate (PIP2), and poly-unsaturated
fatty acids using patch clamp recordings. Cholesterol depletion from the plasma membrane with
methyl-β-cyclodextrin (M-βCD) transiently increased TMEM16A activity and dampened the
run-down whilst cholesterol enrichment with M-βCD + cholesterol enhanced the run-down.
Also, TMEM16A activity decreased by PIP2 dephosphorylation by the Danio rerio voltage-
sensitive phosphatase. Application of diC8-PIP2 in inside-out patches avoided rundown and
partially restored channel activity. Changing membrane cholesterol content slowed the current
decay induced by PIP2 dephosphorylation. Finally, we found that membrane enrichment with
oleic, arachidonic, docosahexaenoic, or eicosapentaenoic fatty acids diminished TMEM16A
activity. These results suggest a membrane-delimited protein-lipid interaction mechanism of
TMEM16A regulation. We propose that the regulation of TMEM16A by lipids would influence
several physiological functions critical to mammals.