Triple arginine residues in the proximal C-terminus of TREK K+ channels are critical for biphasic regulation by phosphatidylinositol 4,5-bisphosphate.
Am J Physiol Cell Physiol
; 316(3): C312-C324, 2019 03 01.
Article
en En
| MEDLINE
| ID: mdl-30576235
ABSTRACT
TWIK-related two-pore domain K+ channels (TREKs) are activated by acidic intracellular pH (pHi), membrane stretch, temperature, and arachidonic acid (AA). Phosphatidylinositol 4,5-bisphosphate (PIP2) exerts concentration-dependent biphasic regulations, which have been observed inhibition by high PIP2, activation by partial decrease of PIP2, and inhibition by depletion of PIP2. Consistently, the stimulation of voltage-sensitive PIP2 phosphatase (Dr-VSP) induces initial activation and subsequent inhibition of TREKs. Lys in the proximal C-terminus (pCt) is responsible for the inhibition by high PIP2, which is generated by phosphatidylinositol kinases with ATP; its neutralizing mutation [K330A of human TREK-2 (hTREK-2)] induces tonic high activity, irrespective of ATP. Here we focus on triple successive Arg in pCt (R3-pCt) as a candidate region for the stimulatory regulation by lower PIP2. Their neutralized mutant (R3A-pCt; RRR340-2A and RRR355-7A in hTREK-1 and -2, respectively) showed negligible basal current and was not affected by ATP removal or by Dr-VSP activation. Phosphatidic acid, a phospholipid agonist of TREKs, did not activate R3A-pCt. In contrast, acidic pHi, AA, and high temperature activated R3A-pCt normally, whereas activation by membrane stretch was attenuated. In hTREK-2, combined neutralizations of the inhibitory K330 and R3-pCt (K330A/RRR355-7A) did not recover the suppressed current. In contrast, combined neutralization of pHi-sensing Glu (E332A/R355-7A) induced tonic high current and no further activation by pHi. Interestingly, when the Gly between K330/E332 and R3-pCt was mutated (G334A), hTREK-2 was tonic activated with reversed responses to ATP and acidic pHi. Therefore, we propose that the PIP2-dependent converse regulation of TREKs by Lys and R3-pCt with Gly implies structural flexibility.
Palabras clave
Texto completo:
1
Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Arginina
/
Fosfatidilinositol 4,5-Difosfato
/
Canales de Potasio de Dominio Poro en Tándem
Límite:
Humans
Idioma:
En
Revista:
Am J Physiol Cell Physiol
Asunto de la revista:
FISIOLOGIA
Año:
2019
Tipo del documento:
Article
País de afiliación:
Corea del Sur