Anti-ORAI1 (N-terminal) polyclonal antibody

Angiotensin II (Ang II) is an oligopeptide of the renin-angiotensin system, and Ang II-induced vascular smooth muscle cell (VSMC) proliferation is an important pathophysiological process involved in atherosclerosis; however, the underlying mechanism remains unclear. Orai1 and Stim1 are the main components of store-operated Ca2+ entry (SOCE), which has an important effect on VSMC proliferation. In the present study, we showed that Ang II-induced human coronary smooth muscle cell (HCSMC) proliferation was associated with increased calcium entry. The expression of Orai1, but not that of Stim1, was significantly upregulated in Ang II-treated HCSMCs. However, knockdown of Orai1 or Stim1 decreased HCSMC proliferation and SOCE activity in Ang II-treated HCSMCs. Orai1 was significantly downregulated in HCSMCs transfected with short interfering RNA (siRNA) against NOX2 or NF-kappa B. Transfection with siRNA against NOX2 or p65 also decreased Ang II-induced HCSMCs SOCE activation and proliferation. These findings suggested that Ang II upregulated Orai1 via the NF-kappa B and NOX2 pathways, leading to increased SOCE and HCSMC proliferation. The molecular factors mediating Ang II-induced SOCE upregulation are potential therapeutic targets for the prevention of Ang II-sensitive or Ang II-dependent HCSMC proliferation.

Store-operated Ca2+ entry through Orai1 channels is a primary mechanism for Ca2+ entry in many cells and mediates numerous cellular effector functions ranging from gene transcription to exocytosis. Orai1 channels are amongst the most Ca2+-selective channels known and are activated by direct physical interactions with the endoplasmic reticulum Ca2+ sensor stromal interaction molecule 1 (STIM1) in response to store depletion triggered by stimulation of a variety of cell surface G-protein coupled and tyrosine kinase receptors. Work in the last decade has revealed that the Orai1 gating process is highly cooperative and strongly allosteric, likely driven by a wave of interdependent conformational changes throughout the protein originating in the peripheral C-terminal ligand binding site and culminating in pore opening. In this review, we survey the structural and molecular features in Orai1 that contribute to channel gating and consider how they give rise to the unique biophysical fingerprint of Orai1 currents.