Transcriptomic characterization of Lonrf1 at the single-cell level under pathophysiological conditions

The LONRF family of proteins consists of three isozymes, LONRF1–3, which harbors RING (really interesting new gene) domain and Lon substrate binding domain. We have recently identified LONRF2 as a protein quality control ubiquitin ligase that acts predominantly in neurons. LONRF2 selectively ubiquitylates misfolded or damaged proteins for degradation. LONRF2(−/−) mice exhibit late-onset neurological deficits. However, the physiological implications of other LONRF isozymes remain unclear. Here, we analysed Lonrf1 expression and transcriptomics at the single-cell level under normal and pathological conditions. We found that Lonrf1 was ubiquitously expressed in different tissues. Its expression in LSEC and Kupffer cells increased with age in the liver. Lonrf1(high) Kupffer cells showed activation of regulatory pathways of peptidase activity. In normal and NASH (nonalcoholic steatohepatitis) liver, Lonrf1(high) LSECs showed activation of NF-kB and p53 pathways and suppression of IFNa, IFNg and proteasome signalling independent of p16 expression. During wound healing, Lonrf1(high)/p16(low) fibroblasts showed activation of cell growth and suppression of TGFb and BMP (bone morphogenetic protein) signalling, whereas Lonrf1(high)/p16(high) fibroblasts showed activation of WNT (wingless and Int-1) signalling. These results suggest that although Lonrf1 does not seem to be associated with senescence induction and phenotypes, LONRF1 may play a key role in linking oxidative damage responses and tissue remodelling during wound healing in different modes in senescent and nonsenescent cells.