Amino Acid Analogs Activate NF-κB through Redox-dependent IκB-α Degradation by the Proteasome without Apparent IκB-α Phosphorylation

We report here that amino acid analogs, which activate hsp70 promoter, are powerful transcriptional activators of human immunodeficiency virus 1 (HIV-1) long terminal repeat (LTR), an activation which was impaired when the two kappaB sites present in the LTR were mutated or deleted. Amino acid analogs also stimulated the transcription of a kappaB-controlled reporter gene. Upon treatment with amino acid analogs, the two NF-kappaB subunits (p65 and p50), which are characterized by a relatively long half-life, redistributed into the nucleus where they bound to kappaB elements. This phenomenon, which began to be detectable after 1 h of treatment, was concomitant with the degradation of the short lived inhibitory subunit IkappaB-alpha by the proteasome. However, contrasting with other NF-kappaB inducers that trigger IkappaB-alpha degradation through a phosphorylation step, amino acid analogs did not change IkappaB-alpha isoform composition. Antioxidant conditions inhibited amino acid analog stimulatory action toward NF-kappaB. This suggests that aberrant protein conformation probably generates a pro-oxidant state that is necessary for IkappaB-alpha proteolysis by the proteasome. Moreover, this activation of NF-kappaB appeared different from that mediated by endoplasmic reticulum overload as it was not inhibited by calcium chelation.