Humanin decreases mitochondrial membrane permeability by inhibiting the membrane association and oligomerization of Bax and Bid proteins

Authors: Ze-wei MA1,2, Dong-xiang LIU1,2
1 Department of Pharmacology III, Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
2 University of Chinese Academy of Sciences, Beijing 100049, China
Corresponding to: Dong-xiang LIU:,
DOI: 10.1038/aps.2017.169
Received: 27 May 2017
Accepted: 18 October 2017
Advance online: 21 December 2017


Humanin (HN) is a 24-residue peptide identified from the brain of a patient with Alzheimer’s disease (AD). HN has been found to protect against neuronal insult caused by Aβ peptides or transfection of familial AD mutant genes. In order to elucidate the molecular mechanisms of HN neuroprotection, we explored the effects of HN on the association of Bax or Bid with lipid bilayers and their oligomerization in the membrane. By using single-molecule fluorescence and Förster resonance energy transfer techniques, we showed that Bax was mainly present as monomers, dimers and tetramers in lipid bilayers, while truncated Bid (tBid) enhanced the membrane association and tetramerization of Bax. HN (100 nmol/L) inhibited the self-association and tBid-activated association of Bax with the bilayers, and significantly decreased the proportion of Bax in tetramers. Furthermore, HN inhibited Bid translocation to lipid bilayers. HN could bind with Bax and Bid either in solution or in the membrane. However, HN could not pull the proteins out of the membrane. Based on these results, we propose that HN binds to Bax and cBid in solution and inhibits their translocation to the membrane. Meanwhile, HN interacts with the membrane-bound Bax and tBid, preventing the recruitment of cytosolic Bax and its oligomerization in the membrane. In this way, HN inhibits Bax pore formation in mitochondrial outer membrane and suppresses cytochrome c release and mitochondria-dependent apoptosis.
Keywords: Alzheimer’s disease; humanin; Bcl-2 family; mitochondrial outer membrane; single-molecule fluorescence