We have cloned four human cDNAs encoding putative cysteine proteinases that have been tentatively called autophagins. These proteins are similar to Apg4/Aut2, a yeast enzyme involved in the activation of Apg8/Aut7 during the process of autophagy. The identified proteins ranging in length from 393 to 474 amino acids also contain several structural features characteristic of cysteine proteinases including a conserved cysteine residue that is essential for the catalytic properties of these enzymes. Northern blot analysis demonstrated that autophagins are broadly distributed in human tissues, being especially abundant in skeletal muscle. Functional and morphological analysis in autophagy-defective yeast strains lacking Apg4/Aut2 revealed that human autophagins-1 and -3 were able to complement the deficiency in the yeast protease, restoring the phenotypic and biochemical characteristics of autophagic cells. Enzymatic studies performed with autophagin-3, the most widely expressed human autophagin, revealed that the recombinant protein hydrolyzed the synthetic substrate Mca-Thr-Phe-Gly-Met-Dpa-NH 2 whose sequence derives from that present around the Apg4 cleavage site in yeast Apg8/Aut7. This proteolytic activity was diminished by N-ethylmaleimide, an inhibitor of cysteine proteases including yeast Apg4/Aut2. These results provide additional evidence that the autophagic process widely studied in yeast can also be fully reconstituted in human tissues and open the possibility to explore the relevance of the autophagin-based proteolytic system in the induction, regulation, and execution of autophagy.Proteolytic enzymes, through their ability to catalyze irreversible hydrolytic reactions, play crucial roles in the development and maintenance of all living organisms (1). Proteases were initially characterized as nonspecific degradative enzymes associated with protein catabolism, but recent studies have demonstrated that they influence a wide range of cellular functions by processing multiple bioactive molecules. These essential processes initiated, regulated, or terminated by proteases include DNA replication, cell-cycle progression, cell proliferation, differentiation and migration, morphogenesis and tissue remodeling, and angiogenesis and apoptosis (1). An additional process in which proteolytic enzymes have also been recently implicated is autophagy (2-4).Autophagy is a biological process involved in the intracellular destruction of endogenous proteins and the removal of damaged organelles and has been suggested to be essential for cell homeostasis as well as for cell remodeling during differentiation, metamorphosis, non-apoptotic cell death, and aging (3-6). In addition, autophagy has also been associated with diverse pathological conditions. Thus, the reduced levels of autophagy have been described in some malignant tumors, and a role for autophagy in controlling the unregulated cell growth linked to cancer has been proposed (7). A deficiency in autophagy has also been found in heart diseases such as Danon cardiomyopat...

We report the cloning of a gene from the human fungal pathogen Candida albicans with sequence and functional similarity to the Saccharomyces cerevisiae SIR2 gene. Deletion of the gene in C.albicans produces a dramatic phenotype: variant colony morphologies arise at frequencies as high as 1 in 10. The morphologies resemble those described previously as part of a phenotypic switching system proposed to contribute to pathogenesis. Deletion of SIR2 also produces a high frequency of karyotypic changes. These and other results are consistent with a model whereby Sir2 controls phenotypic switching and chromosome stability in C.albicans by organizing chromatin structure.

Human collagenase-3 (MMP-13) is a member of the matrix metalloproteinase family of enzymes that was originally identified in breast carcinomas and subsequently detected during fetal ossification and in arthritic processes. In this work, we have found that collagenase-3 is produced by HCS-2/8 human chondrosarcoma cells. An analysis of the ability of different cytokines and growth factors to induce the expression of collagenase-3 in these cells revealed that basic fibroblast growth factor (bFGF or FGF-2) strongly up-regulated the expression of this gene. By contrast, other factors, including interleukin-1beta and transforming growth factor-beta, previously found to induce collagenase-3 expression in other cell types, did not exhibit any effect on the expression of this gene in chondrosarcoma cells. Further analysis of the bFGF-induced expression of collagenase-3 in human chondrosarcoma cells revealed that its effect was time and dose dependent, but independent of the de novo synthesis of proteins. Western blot analysis revealed that the up-regulatory effect of bFGF on collagenase-3 was also reflected at the protein level as demonstrated by the increase of immunoreactive protein in the conditioned medium of HCS-2/8 cells treated with bFGF. Immunohistochemical analysis of the presence of collagenase-3 in a series of 8 benign and 16 malignant cartilage-forming neoplasms revealed that all analyzed malignant chondrosarcomas stained positively for collagenase-3, whereas only 2 of 8 benign lesions produced this protease. In addition, the finding that bFGF was detected in all analyzed chondrosarcomas, together with the above in vitro studies on HCS-2/8 cells, suggest that this growth factor may be an in vivo modulator of collagenase-3 expression in these malignant tumors. These results extend the pattern of tumor types with ability to produce this matrix metalloproteinase and suggest that collagenase-3 upregulation may contribute to the progression of human chondrosarcomas.

Several matrix metalloproteinases (MMPs) have been implicated in intestinal inflammation, mucosal wound healing, and cancer progression. The purpose of this study was to examine the cellular location and putative function of MMP-19, MMP-26 (matrilysin-2), and MMP-28 (epilysin), in normal, inflammatory, and malignant conditions of the intestine. Peroperative tissue specimens from patients with ulcerative colitis (UC) (n = 16) and archival tissue samples of ischemic colitis (n = 9), Crohn's disease (n = 7), UC (n = 8), colon cancer (n = 20), and healthy intestine (n = 5) were examined using immunohistochemical analyses with polyclonal antibodies. Unlike many classical MMPs, MMP-19, MMP-26, and MMP-28 were all expressed in normal intestine. In inflammatory bowel disease (IBD), MMP- 19 was expressed in nonmigrating enterocytes and shedding epithelium. MMP-26 was detected in migrating enterocytes, unlike MMP-28. In colon carcinomas, MMP-19 and MMP-28 expression was downregulated in tumor epithelium. Staining for MMP-26 revealed a meshwork-like pattern between cancer islets, which was absent from most dedifferentiated areas. Our results suggest that MMP-19 is involved in epithelial proliferation and MMP-26 in enterocyte migration, while MMP-28 expression is not associated with inflammatory and destructive changes seen in IBD. In contrast to many previously characterized MMPs, MMP-19 and MMP-28 are downregulated during malignant transformation of the colon and may play a prominent role in tissue homeostasis.

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