Interleukin-1 beta released by gp120 drives neural death through tyrosine phosphorylation and trafficking of NMDA receptors

Interleukin-1 beta is a proinflammatory cytokine implicated under pathological conditions involving NMDA receptor activation, including the AIDS dementia complex (HAD). No information is available on the molecular mechanisms recruited by native interleukin-1 beta produced under this type of condition. Using a sandwich co-culture of primary hippocampal neurons and glia, we investigated whether native interleukin-1 beta released by HIV-gp120-activated glia (i) affects NMDAR functions and (ii) the relevance on neuronal spine density and survival, two specific traits of HAD. Increased phosphorylation of NR2B Tyr-1472 was observed after 24 h of exposure of neurons to 600 pM gp120. This effect occurred only when neurons were treated in the presence of glial cells and was abolished by the interleukin-1 receptor antagonist (IL-1ra). Gp120-induced phosphorylation of NR2B resulted in a sustained elevation of intracellular Ca2+ in neurons and in a significant increase of NR2B binding to PSD95. Increased intracellular Ca2+ was prevented by 10 mu M ifenprodil, that selectively inhibits receptors containing the NR2B, by interleukin-1ra and by Ca-pYEEIE, a Src family SH2 inhibitor peptide. These last two inhibitors, prevented also NR2B binding to PSD95. Finally, gp120 reduced by 35% of the total PSD95 positive spine density after 48 h of treatment and induced by 30% of the neuronal death. Again, both of these effects were blocked by Ca-pYEEIE. Altogether, our data show that gp120 releasing interleukin-1 beta from glia increases tyrosine phosphorylation of NMDAR. Thus, tyrosine phosphorylation may contribute to the sensitization of the receptor increasing its function and synaptic localization. Both of these effects are relevant for neurodegeneration.