The growth-related gene product β (GROβ) is a small chemoattractant cytokine that belongs to the CXC chemokine family, and GROβ receptors are expressed in the brain, including the cerebellum. We demonstrate that rat cerebellar granule neurones express the GROβ receptor CXCR2. We also show that, in addition to the known stimulation of a phosphoinositide-specific phospholipase C, GROβ activates both neutral (N-) and acidic (A-) sphingomyelinases (SMase) and the stress-activated c-Jun N-terminal kinase 1 (JNK1). Although both exogenous ceramide and bacterial SMase stimulate JNK1, GROβ-induced JNK1 activation is an event probably independent of ceramide generated by A-SMase, since it is maintained in the presence of compounds that block A-SMase activity. This is the first report on the activation of the SMase pathway by chemokines.
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