Network Topology and Interactomic Analysis Reveal the Regulatory Framework of the Humanin Protein Family (MTRNR2Lx Class).

This study presents an in-depth analysis of an interactome comprising approximately 1033 nodes, focusing on its topology, reliability, and functional implications, with particular attention to the small mitochondrial proteins of the Humanin family and their nuclear-encoded MTRNR2Lx paralogs. The analysis, conducted through stringent high-reliability filters and experimentally supported interaction data, produced a curated network model in which approximately 70% of the retained interactions were supported by experimental evidence, providing a solid basis for network-based functional interpretation. The topology of the interactome showed scale-free and modular network characteristics, with hub and bottleneck nodes defining highly connected stress-response and regulatory modules. Humanin-related proteins, positioned at the periphery of the interactome, emerged as candidate modulatory nodes linking peripheral signaling interfaces to broader functional modules. Mitochondrial Humanin may contribute to early cytoprotective responses, including pathways associated with BAX-dependent apoptosis regulation, whereas nuclear MTRNR2Lx proteins appear to be connected to more sustained regulatory networks involving neuroprotection- and apoptosis-associated modules under chronic stress conditions. In particular, the MTRNR2Lx-FPR2/G-protein module, including GNB1, emerged as a candidate signaling interface that may contribute to the downstream organization of Humanin-related responses. This network-based distinction supports the view that Humanin-family peptides may operate as modulators of stress-response networks rather than as isolated effectors of intrinsic mitochondrial functions. Overall, the methodological approach, results, and proposed model provide new insights into the systems-level organization of Humanin biology and identify prioritized molecular candidates for future in vitro and in vivo validation in the context of neurodegeneration, apoptosis, and cellular stress.