Characterization of β‐glucan Treated Human Neutrophils Provides a Phospho‐Site Specific Global Proteomic Analysis of Downstream Phosphorylation Events

Although the innate immune system has been studied for a number of years, a well‐defined pharmacological intervention able to beneficially prime immune cell function is still unavailable. This is so because the favorable aspects of immune priming needed to improve host defense are accompanied by the overproduction of proinflammatory mediators at levels that cannot be tolerated by human subjects. A nonphlogistic preparation of β‐glucan has shown that the antimicrobial functions of host immune cells can be enhanced in the absence of excess cytokine production. We generated a global phosphoproteomic analysis of human neutrophils in the presence or absence of IMPRIME‐PGG‐β‐glucan. Tandom mass spectrometry was used to provide peptide identification and quantification by performing a survey scan in the FT‐ICR followed by data‐dependent MS/MS scans of the nine most abundant ions in the LTQ. A total of 118 phosphopeptides were significantly regulated by β‐glucan (p<0.05). Of these phosphopeptides, 82 decreased by 2‐fold or greater, 33 decreased within 2‐fold, 2 increased by 2‐fold or greater, and 1 increased within 2‐fold. A number of proteins revealed multiple phosphorylation sites. Together these findings begin to define an intracellular mechanism of action for IMPRIME‐PGG‐β‐glucan on neutrophil priming. NIH GM066194