Thrombin-induced growth cone collapse: Involvement of phospholipase A(2) and eicosanoid generation

The studies presented here explore intracellular signals resulting from the action of repellents on growth cones. Growth cone challenge with thrombin or thrombin receptor-activating peptide (TRAP) triggers collapse via a rece ptor-mediated process. The results indicate that this involves activation o f cytosolic phospholipase A(2) (PLA(2)) and eicosanoid synthesis. The colla pse response to repellents targets at least two functional units of the gro wth cone, the actin cytoskeleton and substratum adhesion sites. We show in a cell-free assay that thrombin and TRAP cause the detachment of isolated g rowth cones from laminin. Biochemical analyses of isolated growth cones rev eal that thrombin and TRAP stimulate cytosolic PLA(2) but not phospholipase C. In addition, thrombin stimulates synthesis of 12- and 15-hydroxyeicosat etraenoic acid (HETE) from the released arachidonic acid via a lipoxygenase (LO) pathway. A selective LO inhibitor blocks 12/15-HETE synthesis in grow th cones and inhibits thrombin-induced growth cone collapse. Exogenously ap plied 12(S)-HETE mimics the thrombin effect and induces growth cone collaps e in culture. These observations indicate that thrombin-induced growth cone collapse occurs by a mechanism that involves the activation of cytosolic P LA(2) and the generation of 12/15-HETE.