The mouse ortholog of human FACE-1, Zmpste24, is a multispanning membrane protein widely distributed in mammalian tissues 1,2 and structurally related to Afc1p/ste24p, a yeast metalloproteinase involved in the maturation of fungal pheromones 3 . Disruption of the gene Zmpste24 caused severe growth retardation and premature death in homozygous-null mice. Histopathological analysis of the mutant mice revealed several abnormalities, including dilated cardiomyopathy, muscular dystrophy and lipodystrophy. These alterations are similar to those developed by mice deficient in A-type lamin 4 , a major component of the nuclear lamina 5 , and phenocopy most defects observed in humans with diverse congenital laminopathies 6-8 . In agreement with this finding, Zmpste24-null mice are defective in the proteolytic processing of prelamin A. This deficiency in prelamin A maturation leads to the generation of abnormalities in nuclear architecture that probably underlie the many phenotypes observed in both mice and humans with mutations in the lamin A gene. These results indicate that prelamin A is a specific substrate for Zmpste24 and demonstrate the usefulness of genetic approaches for identifying the in vivo substrates of proteolytic enzymes.To clarify the function of Zmpste24, and to identify in vivo substrates targeted by this proteinase, we generated Zmpste24-null mice (Fig. 1a). After heterozygote intercrossing, we obtained Zmpste24-null, heterozygous and wildtype mice in the expected mendelian ratio. We verified homozygosity with respect to the mutated allele by Southern blot (Fig. 1b), and lack of Zmpste24 Fig. 1 Generation of Zmpste24-deficient mice. a, Schematic representation of the wildtype Zmpste24 locus (WT), targeting vector and targeted allele (KO). Positions of restriction enzyme sites and probes used for Southern-blot analysis are shown. b, Southern-blot analysis of genomic DNA from three littermate progeny of Zmpste24 heterozygote crosses. Probing of EcoRI-digested DNA revealed fragments of 6 kb and 4 kb for wildtype and disrupted alleles, respectively. Probing of BamHI-digested DNA revealed fragments of 10 kb and 8 kb for wildtype and disrupted alleles, respectively. c, Extracts of kidneys from wildtype and Zmpste24 -/-mice were examined with a monoclonal antibody directed against the C terminus of Zmpste24. d, Photograph of two littermate progeny of a Zmpste24 heterozygote cross, at 3 mo. e, Radiograph of a Zmpste24 -/-mouse at 3 mo, compared with a wildtype control. f, Cumulative plot of body weight versus age. Dots represent mean values, and error bars indicate s.e.m.

Zmpste24 (also called FACE-1) is a metalloproteinase involved in the maturation of lamin A (Lmna), an essential component of the nuclear envelope. Both Zmpste24- and Lmna-deficient mice exhibit profound nuclear architecture abnormalities and multiple histopathological defects that phenocopy an accelerated ageing process. Similarly, diverse human progeroid syndromes are caused by mutations in ZMPSTE24 or LMNA genes. To elucidate the molecular mechanisms underlying these devastating diseases, we have analysed the transcriptional alterations occurring in tissues from Zmpste24-deficient mice. We demonstrate that Zmpste24 deficiency elicits a stress signalling pathway that is evidenced by a marked upregulation of p53 target genes, and accompanied by a senescence phenotype at the cellular level and accelerated ageing at the organismal level. These phenotypes are largely rescued in Zmpste24-/-Lmna+/- mice and partially reversed in Zmpste24-/-p53-/- mice. These findings provide evidence for the existence of a checkpoint response activated by the nuclear abnormalities caused by prelamin A accumulation, and support the concept that hyperactivation of the tumour suppressor p53 may cause accelerated ageing.

22 secondary bile acids as a possible mechanism for the beneficial effects of reestablishing 51 a healthy microbiome. Our results demonstrate that correction of the accelerated aging-52 associated intestinal dysbiosis is beneficial, suggesting the existence of a link between 53 aging and the gut microbiota that provides a rationale for microbiome-based interventions 54 against age-related diseases. 55 56 57

Proteolytic events at the cell surface are essential in the regulation of signal transduction pathways. During the past years, the family of type II transmembrane serine proteases (TTSPs) has acquired an increasing relevance because of their privileged localization at the cell surface, although our current understanding of the biologic function of most TTSPs is limited. Here we show that matriptase-2 (Tmprss6), a recently described member of the TTSP family, is an essential regulator of iron homeostasis. Thus, Tmprss6 Ϫ/Ϫ mice display an overt phenotype of alopecia and a severe iron deficiency anemia. These hematologic alterations found in Tmprss6 Ϫ/Ϫ mice are accompanied by a marked up-regulation of hepcidin, a negative regulator of iron export into plasma. Likewise, Tmprss6 Ϫ/Ϫ mice have reduced ferroportin expression in the basolateral membrane of enterocytes and accumulate iron in these cells. Iron-dextran therapy rescues both alopecia and hematologic alterations of Tmprss6 Ϫ/Ϫ mice, providing causal evidence that the anemic phenotype of these mutant mice results from the blockade of intestinal iron export into plasma after dietary absorption. On the basis of these findings, we conclude that matriptase-2 activity represents a novel and relevant step in hepcidin regulation and iron homeostasis. IntroductionPericellular proteolysis is an essential event that determines the relations between the cell and its microenvironment. This crucial process in the development and maintenance of multicellular organisms requires the remodeling of extracellular matrix components as well as the posttranslational regulation of a wide range of cell-surface receptors, regulatory proteins, and adhesion molecules. 1 The increasing relevance of proteolytic processes localized at the cell surface has attracted notable attention on membraneassociated proteolytic systems, including the family of type II transmembrane serine proteases (TTSPs). 2,3 The TTSP family is composed of more than 20 different members that share a number of structural features: a single-pass transmembrane domain located near the short cytoplasmic amino-terminal tail, a central region containing different protein-interacting domains, and a carboxyterminal catalytic region with the structural characteristics of serine proteases. The large variability of the central modular region together with the diverse expression patterns of TTSP family members suggest that these enzymes may play different physiologic and pathologic roles, although only a few of these functions have been identified so far. Thus, enteropeptidase is mainly expressed in the duodenum and plays an essential role in food digestion as activator of pancreatic trypsinogen to trypsin. 4 Hepsin, is mainly expressed in liver, but it is highly up-regulated in prostate cancer. 5,6 Matriptase/MT-SP1 is a widely studied member of the TTSP family because of its relevance in diverse processes, including cancer progression. 7,8 Mutant mice deficient in matriptase die shortly after birth because of aberrant skin ...

We generated mice deficient in Lon protease (LONP1), a major enzyme of the mitochondrial quality control machinery. Homozygous deletion of Lonp1 causes early embryonic lethality, whereas its haploinsufficiency protects against colorectal and skin tumors. Furthermore, LONP1 knockdown inhibits cellular proliferation and tumor and metastasis formation, whereas its overexpression increases tumorigenesis. Clinical studies indicate that high levels of LONP1 are a poor prognosis marker in human colorectal cancer and melanoma. Additionally, functional analyses show that LONP1 plays a key role in metabolic reprogramming by remodeling OXPHOS complexes and protecting against senescence. Our findings demonstrate the relevance of LONP1 for cellular and organismal viability and identify this protease as a central regulator of mitochondrial activity in oncogenesis.