Aspirin and salicylate bind to immunoglobulin heavy chain binding protein (BiP) and inhibit its ATPase activity in human fibroblasts

Salicylic acid (SA), an endogenous signaling molecule of plants, possesses anti-inflammatory and anti-neoplastic actions in human. Its derivative, asp irin, is the most commonly used anti-inflammatory and analgesic drug. Aspir in and sodium salicylate (salicylates) have been reported to have multiple pharmacological actions. However, it is unclear whether they bind to a cell ular protein. Here, we report for the first time the purification from huma n fibroblasts of a similar to 78 kDa salicylate binding protein with sequen ce identity to immunoglobulin heavy chain binding protein (BiP). The K-d va lues of SA binding to crude extract and to recombinant BiP were 45.2 and 54 .6 muM, respectively. BiP is a chaperone protein containing a polypeptide b inding site recognizing specific heptapeptide sequence and an ATP binding s ite. A heptapeptide with the specific sequence displaced SA binding in a co ncentration-dependent manner whereas a control heptapeptide did not. Salicy lates inhibited ATPase activity stimulated by this specific heptapeptide bu t did not block ATP binding or induce BiP expression. These results indicat e that salicylates bind specifically to the polypeptide binding site of BiP in human cells that may interfere with folding and transport of proteins i mportant in inflammation.