For example, pharmacologic levels of two PIs that are clinically linked to osteopenia, ritonavir (RTV) and saquinavir (SQV) but not indinavir (IDV) and nelfinavir (NFV), abolish the interferon-γ-mediated degradation of the RANKL signaling adapter protein TRAF6 (tumor necrosis factor receptor-associated protein 6) in proteasomes. The gene discussed is TNFSF11; the disease is Osteopenia.