Activation of PKA and Epac proteins by cyclic AMP depletes intracellular calcium stores and reduces calcium availability for vasoconstriction

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• 作者：Andrea Cuí ; ñ ; as ; Veró ; nica Garcí ; a-Morales ; Dolores Viñ ; a ; José ; Gil-Longo ; Manuel Campos-Toimil ; ^{manuel.campos@usc.es" class="auth_mail" title="E-mail the corresponding author}
• 关键词：AVP ; arginine-vasopressin ; [Ca2  ; +]c ; cytoplasmic Ca2  ; + concentration ; cAMP ; 3&prime ; 5&prime ; -cyclic adenosine monophosphate ; db-cAMP ; dibutyryl cyclic AMP ; DMSO ; dimethyl sulfoxide ; Epac ; exchange protein directly activated by cAMP ; FBS ; foetal bovine serum ; KBS ; Krebs bicarbonate solution ; PKA ; cyclic-AMP protein kinase ; RASMC ; rat aortic smooth muscle cells ; SERCA ; sarcoplasmic/endoplasmic reticulum Ca2  ; +-ATPase ; SOCE ; store-operated Ca2  ; + entry ; VOCC ; voltage-operated Ca2
• 刊名：Life Sciences
• 出版年：2016
• 出版时间：15 June 2016
• 年：2016
• 卷：155
• 期：Complete
• 页码：102-109
• 全文大小：729 K

文摘

We investigated the implication of PKA and Epac proteins in the endothelium-independent vasorelaxant effects of cyclic AMP (cAMP).

Main methods

Cytosolic Ca^2 + concentration ([Ca^2 +]_c) was measured by fura-2 imaging in rat aortic smooth muscle cells (RASMC). Contraction-relaxation experiments were performed in rat aortic rings deprived of endothelium.

Key findings

In extracellular Ca^2 +-free solution, cAMP-elevating agents induced an increase in [Ca^2 +]_c in RASMC that was reproduced by PKA and Epac activation and reduced after depletion of intracellular Ca^2 + reservoirs. Arginine-vasopressin (AVP)-evoked increase of [Ca^2 +]_c and store-operated Ca^2 + entry (SOCE) were inhibited by cAMP-elevating agents, PKA or Epac activation in these cells. In aortic rings, the contractions induced by phenylephrine in absence of extracellular Ca^2 + were inhibited by cAMP-elevating agents, PKA or Epac activation. In these conditions, reintroduction of Ca^2 + induced a contraction that was inhibited by cAMP-elevating agents, an effect reduced by PKA inhibition and reproduced by PKA or Epac activators.

Significance

Our results suggest that increased cAMP depletes intracellular, thapsigargin-sensitive Ca^2 + stores through activation of PKA and Epac in RASMC, thus reducing the amount of Ca^2 + released by IP₃-generating agonists during the contraction of rat aorta. cAMP rise also inhibits the contraction induced by depletion of intracellular Ca^2 +, an effect mediated by reduction of SOCE after PKA or Epac activation. Both effects participate in the cAMP-induced endothelium-independent vasorelaxation.