PROJECT SUMMARY Maintenance of proper mitochondrial function is critical to organismal health. Mitochondrial stress contributes to ageing and the pathogenesis of numerous diseases. Intracellular insults, such as oxidative stress, mitochondrial DNA mutations, and disrupted interactions with other organelles including lysosomes and the endoplasmic reticulum are relatively well identified inducers of mitochondrial dysfunction. Yet it remains largely elusive how mitochondrial homeostasis can be altered upon changes in cellular microenvironment, the extracellular matrix (ECM). In mammals, ECM remodeling occurs during aging and in multiple diseases including infections, cancers, and neurodegeneration. The remodeled ECM may liberate bioactive fragments that can promote tissue damage- related responses, such as wound healing and inflammation. TMEM2 is a plasma membrane-bound hyaluronidase that cleaves hyaluronan, a major glycosaminoglycan constituent of the ECM in vertebrates. We discovered that TMEM2 induces mitochondrial stress responses in both human cells and nematodes, suggesting a novel conserved link between the ECM and mitochondria. In aim 1 and 2 of this proposal, we will systemically characterize TMEM2-induced global changes on mitochondria, determine what specific changes to the ECM are causative of these changes, and identify essential genetic regulators of the pathway in mammals and nematodes. Both aging and infection are associated with profound changes in the ECM. We observed that TMEM2 promotes longevity and immunity in nematodes, most likely due to changes to the ECM. We hypothesize that TMEM2- induced ECM degradation may be sensed as a signal of tissue damage mimicking infection or other environmental stress, which may elicit mitochondrial stress to potentiate mitochondrial stress responses and innate immune responses, and eventually prolong the lifespan due to these protective stress responses. In aim 3, we will test whether TMEM2-induced longevity is mediated by mitochondrial signaling, and whether the ECM- mitochondria signaling may be involved in immune responses during infection. Moreover, we will perform mass spectrometry as well as functional genomic screens to systemically assess the role of ECM remodeling in regulating mitochondrial homeostasis during aging.