A novel chimeric aequorin fused with caveolin-1 reveals a sphingosine kinase 1-regulated Ca2+ microdomain in the caveolar compartment

作者：Pulli Ilari; Blom Tomas; Lof Christoffer; Magnusson Melissa; Rimessi Alessandro; Pinton Paolo; Tornquist Kid^*

来源：Biochimica et Biophysica Acta-Molecular Cell Research, 2015, 1853(9): 2173-2182.

DOI：10.1016/j.bbamcr.2015.04.005

• Caveolin-1
• Aequorin
• Sphingosine kinase 1
• Sphingosine-1-phosphate
• Calcium
• Plasma membrane

Caveolae are plasma membrane invaginations enriched in sterols and sphingolipids. Sphingosine kinase 1 (SK1) is an oncogenic protein that converts sphingosine to sphingosine 1-phosphate (S1P), which is a messenger molecule involved in calcium signaling. Caveolae contain calcium responsive proteins, but the effects of SK1 or S1P on caveolar calcium signaling have not been investigated. We generated a Caveolin-1-Aequorin fusion protein (Cav1-Aeq) that can be employed for monitoring the local calcium concentration at the caveolae ([Ca2+]cav). In HeLa cells, Cav1-Aeq reported different [Ca2+] as compared to the plasma membrane [Ca2+] in general (reported by SNAP25-Aeq) or as compared to the cytosolic [Ca2+] (reported by cyt-Aeq). The Ca2+ signals detected by Cav1-Aeq were significantly attenuated when the caveolar structures were disrupted by methyl-beta-cyclodextrin, suggesting that the caveolae are specific targets for Ca2+ signaling. HeLa cells overexpressing SK1 showed increased [Ce2+]cav during histamine-induced Ca2+ mobilization in the absence of extracellular Ca2+ as well as during receptor-operated Ca2+ entry (ROCE). The SK1-induced increase in [Ca2+]cav during ROCE was reverted by S1P receptor antagonists. In accordance, pharmacologic inhibition of SK1 reduced the [Ca2+]cav during ROCE. S1P treatment stimulated the [Ca2+]cav upon ROCE. The Ca2+ responses at the plasma membrane in general were not affected by SK1 expression. In summary, our results show that SK1/S1P-signaling regulates Ca2+ signals at the caveolae. This article is part of a Special Issue entitled: 13th European Symposium on Calcium.

• 出版日期2015-9
• 单位河北医科大学