Mitochondrial health is increasingly recognized as a cornerstone of reproductive biology, yet the molecular switches that trigger mitochondrial proliferation inside ovarian follicles have remained poorly understood. New findings published in PNAS illuminate a surprisingly elegant mechanism: lactate, long dismissed as a metabolic waste product, acts as a chemical messenger that modifies the chaperone protein HSP90α in a process called lactylation, ultimately directing the energy-generating machinery of granulosa cells to expand.
The research demonstrates that lactylation of HSP90α at specific residues enables the coordinated nuclear translocation of two transcriptional regulators — PGC1α, a well-established master regulator of mitochondrial biogenesis, and LRPGC1, a less-characterized isoform. This dual nuclear entry event activates the transcriptional programs responsible for building new mitochondria within granulosa cells — the somatic cells that surround the developing egg and are essential for both follicle growth and estrogen synthesis. Without functional HSP90α lactylation, mitochondrial biogenesis is blunted, impairing the energy supply and steroidogenic substrate availability that maturing follicles depend on.
This finding sits at the intersection of two rapidly evolving fields: lactate signaling and post-translational modifications as metabolic sensors. Lactylation — the addition of a lactyl group derived from lactate to lysine residues — was only formally described in 2019, and the field is still mapping which proteins it meaningfully regulates. Identifying HSP90α as a functional lactylation target in reproductive tissue adds a consequential data point. For adult health, the implications extend beyond fertility: granulosa cell mitochondrial dysfunction is implicated in age-related ovarian decline, polycystic ovary syndrome, and diminished oocyte quality. Whether pharmacologically modulating HSP90α lactylation could support follicular health in aging ovaries remains speculative, but the mechanistic precision here is notable. This is a genuinely novel molecular pathway, though the work appears to be primarily cell or animal-based, which limits immediate clinical translation.