Mitochondrial Peptides Humanin and SHLP6 Show Signs of Evolutionary Selection
Background
Mitochondrial-derived peptides (MDPs) like humanin and SHLP6 are crucial regulators of cellular metabolism, stress response, and longevity. Humanin is known for its neuroprotective and anti-apoptotic effects, while SHLP6 plays a role in metabolic homeostasis. Despite their recognized importance, there has been a significant gap in understanding the evolutionary pressures and natural selection mechanisms that have shaped the sequences and functions of these critical MDPs across species.
Results
The study revealed a complex evolutionary landscape for both peptides, indicating strong selective pressures. For humanin, ~92% of its codons were found to be under strong purifying selection (mean dN/dS = 0.18), suggesting critical functional conservation across species. However, 3 specific amino acid sites (e.g., codon 12) exhibited clear evidence of positive selection with dN/dS ratios exceeding 3.0, implying adaptive changes. SHLP6 showed a more mosaic pattern, with ~78% of its sequence under purifying selection (mean dN/dS = 0.45) and 2 distinct regions (e.g., N-terminus) displaying positive selection with dN/dS ratios up to 2.7. This indicates that while core functions are conserved, certain regions have adapted to specific environmental or physiological challenges. Both humanin and SHLP6 exhibit a mosaic pattern of strong purifying selection across core functional domains and episodic positive selection at specific sites, highlighting their evolutionary importance and adaptive potential.
Why It Matters
Understanding the evolutionary history and selective pressures on humanin and SHLP6 provides crucial insights into their functional significance and potential roles in health and disease. The identification of sites under positive selection suggests regions that may be critical for species-specific adaptations or novel functions, which could be exploited for therapeutic purposes. This research could inform the rational design of novel peptide mimetics or modulators for conditions like neurodegeneration, metabolic disorders, and age-related diseases, by targeting these evolutionarily significant regions. Future steps include functional validation of these identified sites in in vitro and in vivo models.