Mass spectrometric phosphoproteome analysis of HIV-infected brain reveals novel phosphorylation sites and differential phosphorylation patterns

PurposeTo map the phosphoproteome and identify changes in the phosphorylation patterns in the HIV-infected and uninfected brain. Experimental designParietal cortex from individuals with and without HIV infection were lysed and trypsinized. The peptides were labeled with iTRAQ reagents, combined, phospho-enriched by titanium dioxide chromatography, and analyzed by LC-MS/MS with high resolution. ResultsOur phosphoproteomic workflow resulted in the identification of 112 phosphorylated proteins and 17 novel phosphorylation sites in all the samples that were analyzed. The phosphopeptide sequences were searched for kinase substrate motifs, which revealed potential kinases involved in important signaling pathways. The site-specific phosphopeptide quantification showed that peptides from neurofilament medium polypeptide, myelin basic protein, and 2-3-cyclic nucleotide-3 phosphodiesterase have relatively higher phosphorylation levels during HIV infection. Conclusions and clinical relevanceThis study has enriched the global phosphoproteome knowledge of the human brain by detecting novel phosphorylation sites on neuronal proteins and identifying differentially phosphorylated brain proteins during HIV infection. Kinases that lead to unusual phosphorylations could be therapeutic targets for the treatment of HIV-associated neurocognitive disorders.