We developed selective monoclonal antibodies against Hsp90 nitrated on Y33 or Y56 and showed that the chaperone is endogenously nitrated on these tyrosine residues in vivo in motor neurons from amyotrophic lateral sclerosis patients and animal models [27], in PC12 cells treated with peroxynitrite [27,28], and in human schwannomas and cell culture models [26]. The gene discussed is HSP90AA1; the disease is schwannoma.