Ceramide kinase uses ceramide provided by ceramide transport protein: localization to organelles of eicosanoid synthesiss⃞

Abstract

Ceramide kinase (CERK) is a critical mediator of eicosanoid synthesis, and its product, ceramide-1-phosphate (C1P), is required for the production of prostaglandins in response to several inflammatory agonists. In this study, mass spectrometry analysis disclosed that the main forms of C1P in cells were C16:0 C1P and C18:0 C1P, suggesting that CERK uses ceramide transported to the trans-Golgi apparatus by ceramide transport protein (CERT). To this end, downregulation of CERT by RNA interference technology dramatically reduced the levels of newly synthesized C1P (kinase-derived) as well as significantly reduced the total mass levels of C1P in cells. Confocal microscopy, subcellular fractionation, and surface plasmon resonance analysis were used to further localize CERK to the trans-Golgi network, placing the generation of C1P in the proper intracellular location for the recruitment of cytosolic phospholipase A2α. In conclusion, these results demonstrate that CERK localizes to areas of eicosanoid synthesis and uses a ceramide “pool” transported in an active manner via CERT.

Keywords

• ceramide-1-phosphate
• prostaglandins
• phospholipase A2
• inflammation
• arachidonic acid