Oxidative Damage? Not a Problem! The Characterization of Humanin-like
Mitochondrial Peptide in Anoxia Tolerant Freshwater Turtles
Abstract
Mitochondria was long thought to be an “end function” organelle that
regulated the metabolic flux and apoptosis in the cell. However, with
the discovery of humanin (HN/MTRNR2), the first mitochondrial peptide in
the early 2000s, the cytoprotective and pro-survival applications of
MDPs have taken the forefront of therapeutic and diagnostic research.
However, the regulation of humanin-like MDPs in natural model systems
that can tolerate lethal environmental and cytotoxic insults remains to
be investigated. Red-eared sliders are champion anaerobes that can
withstand three continuous months of anoxia followed by rapid bouts of
oxygen reperfusion without incurring cellular damage. Freshwater turtles
employ extensive physiological and biochemical strategies to combat
anoxia, with metabolic rate depression and a global enhancement of
antioxidant and cytoprotective pathways being the two most important
contributors. The main aim of this study was to uncover and characterize
the humanin-homologue in freshwater turtles as well as investigate the
differential regulation of humanin in response to short and long-term
oxygen deprivation. In this study we have used de novo and
homology-based protein modelling to elucidate the putative structure of
humanin in red-eared sliders as well as an ELISA and western
immunoblotting to confirm the protein abundance in the turtle brain and
six peripheral tissues during control, 5 h, and 20 h anoxia (n=4/group).
We found that a humanin-homologue (TSE-humanin) is present in red-eared
sliders and it may play a crucial cytoprotective role against oxidative
damage.