Direct binding of sulfur mustard and chloroethyl ethyl sulphide to human cell membrane-associated proteins; implications for sulfur mustard pathology

Sulfur mustard (SM) is a potent vesicating agent that produces debilitating blisters and ulcerating lesions on the skin which are characteristically slow to heal. There are currently no specific medical countermeasures to prevent SM-induced vesication and therefore SM remains a major military threat. To investigate the mechanism by which SM causes these injuries we aimed to identify the cellular proteins that are important in the vesicant response and pathology of SM. Membrane and membrane-associated proteins that are targets for direct binding by SM were compared to targets directly bound by CEES (chloroethylethylsulphide). As CEES is a less potent blistering agent compared to SM, it was hypothesised that differences in the binding of these two mustards could reveal key proteins directly involved in the mustard vesicant response. Human cellular membranes fractionated from HaCaT cells were exposed to 14C-SM or 14C-CEES and the membrane proteins to which SM or CEES bound were separated by 2D gel electrophoresis, located by fluorography and subsequently identified using mass spectrometry. A number of proteins were identified that were differentially labelled by SM and CEES. Actin, annexin A2 and keratin 9 were labelled with SM at a higher intensity than was seen with the same concentration of CEES. Therefore results from these studies suggest that SM binding to these proteins could contribute to the complex pathology seen following SM exposure.