Significance Excitation–transcription (E-T) coupling can initiate and modulate essential physiological or pathological responses in cells, such as neurons and cardiac myocytes. Although vascular myocytes also exhibit E-T coupling in response to membrane depolarization, the underlying molecular mechanisms are unknown. Our study reveals that E-T coupling in vascular myocytes converts intracellular Ca 2+ signals into selective gene transcription related to chemotaxis, leukocyte adhesion, and inflammation. Our discovery identifies a mechanism for vascular remodeling as an adaptation to increased circumferential stretch.

Ca 2+ signaling induces gene transcription and mediates cellular functions in diverse types of cells. In neurons, Ca 2+ influx through voltage-dependent Ca 2+ channels (VDCC) activates Ca 2+ /calmodulin-dependent protein kinases (CaMK), promotes gene transcription and constructs neural networks. This pathway is called excitation-transcription (E-T) coupling. E-T coupling is also reported in vascular smooth muscle cells (VSMC), but its molecular mechanisms and pathophysiological roles are unknown. In VSMCs, caveolin (cav)-1, an essential component of caveolae, forms Ca 2+ microdomains where VDCC and its effectors are accumulated and regulates vascular tone. In the present study, we hypothesized that prolonged VDCC activation in caveolae triggers E-T coupling in VSMC and causes vascular remodeling. When the mesenteric artery was depolarized for longer than 30 min, nuclear CREB phosphorylation and pro-inflammatory gene transcription were promoted. These responses were significantly reduced in cav-1 KO mice. Pharmacological inhibition or siRNA knockdown of CaMKK-CaMK pathway revealed the molecular pathway connecting Ca 2+ influx through VDCC in caveolae and CREB phosphorylation. These results suggest that excessive Ca 2+ signaling in caveolae causes E-T coupling in VSMC and triggers vascular remodeling by upregulating proinflammatory genes.

In smooth muscle cells (SMCs), caveolin (cav)-1, an essential component of caveolae, forms Ca 2+ microdomain accumulating voltage-dependent Ca 2+ channels (VDCC) and ryanodine receptors (RyR). The functional coupling between VDCC and RyR (Ca 2+-induced Ca 2+ release: CICR) causes SMC contraction, i.e. excitation-contraction (E-C) coupling. On the other hand, Ca 2+ influx through VDCC activates Ca 2+ /calmodulin-dependent protein kinase, and promotes gene transcription in neurons, i.e. excitation-transcription (E-T) coupling. E-T coupling is known in SMCs, but its structural basis and physiologic function are unknown. Therefore, we examined the relationships between Ca 2+ microdomain formed by caveolae and E-T coupling in SMCs. When the mesenteric artery was depolarized, the phosphorylation of CREB was detected in the nuclei of SMCs. This response was not observed in tissues from cav-1 KO mice that lack caveolae in SMCs and those in which caveolae were destroyed by methyl beta cyclodextrin. Inhibition of RyR by tetracaine also reduced the CREB phosphorylation. These results suggest that CICR in caveolae is necessary for the E-T coupling in SMCs. Caveolae can control not only SMC contractility but also gene expression by regulating Ca 2+ signaling.

In smooth muscle cells (SMCs), caveolin (cav)-1, an essential component of caveolae, forms Ca 2+ microdomain accumulating voltage-dependent Ca 2+ channels (VDCC) and ryanodine receptors (RyR). The functional coupling between VDCC and RyR causes SMC contraction, i.e. excitation-contraction (E-C) coupling. On the other hand, Ca 2+ influx through VDCC activates Ca 2+ /calmodulin-dependent protein kinase (CaMK), and promotes gene transcription in neurons, i.e. excitation-transcription (E-T) coupling. E-T coupling is known in SMCs, but its structural basis and physiological function are unknown. Therefore, we examined the relationships between Ca 2+ microdomain formed by caveolae and E-T coupling in SMCs. When the mesenteric artery was depolarized, the phosphorylation of CREB in the nuclei of SMCs and induction of c-fos was detected. These responses were not observed in the tissue of Cav-1 KO mouse that lacks caveolae in SMCs and those in which caveolae were destroyed by methyl b cyclodextrin. The CREB phosphorylation was significantly attenuated by a CaMKK2 inhibitor STO609 and CaMK2 inhibitor KN93. Furthermore, fluorescence imaging analyses detected a direct molecular coupling between cav1 and CaMKK2. These results suggest that caveolae accumulate Ca 2+ channels and CaMKK2 and cause not only E-C coupling but also E-T coupling in SMCs.