Maturation and degradation of beta-galactosidase in the post-Golgi compartment are regulated by cathepsin B and a non-cysteine protease

Senescence-Associated β-Galactosidase Detection in Pathology

Activity of β-galactosidase at pH 6 is a classic maker of senescence in cellular biology. Cellular senescence, a state of highly stable cell cycle arrest, is often compared to apoptosis as an intrinsic tumor suppression mechanism. It is also thought that SA-β-gal is crucial in malignant cell transformation. High levels of senescence-associated β-galactosidase (SA-β-gal) can be found in cancer and benign lesions of various localizations making the enzyme a highly promising diagnostic marker for visualization of tumor margins and metastases. These findings facilitate the research of therapy induced senescence as a promising therapeutic strategy. In this review, we address the need to collect and analyze the bulk of clinical and biological data on SA-β-gal mechanisms of action to support wider implementation of this enzyme in medical diagnostics. The review will be of interest to pathologists, biologists, and biotechnologists investigating cellular senescence for purposes of regenerative medicine and oncology.

Methods of detection of β-galactosidase enzyme in living cells

The application of β-galactosidase enzyme ranges from industrial use as probiotics to medically important application such as cancer detection. The irregular activities of β-galactosidase enzyme are directly related to the development of cancers. Identifying the location and expression levels of enzymes in cancer cells have considerable importance in early-stage cancer diagnosis and monitoring the efficacy of therapies. Most importantly, the knowledge of the efficient method of detection of β-galactosidase enzyme will help in the early-stage treatment of the disease. In this review paper, we provide an overview of recent advances in the detection methods of β-galactosidase enzyme in the living cells, including the detection strategies, and approaches in human beings, plants, and microorganisms such as bacteria. Further, we emphasized on the challenges and opportunities in this rapidly developing field of development of different biomarkers and fluorescent probes based on β-galactosidase enzyme. We found that previously used chromo-fluorogenic methods have been mostly replaced by the new molecular probes, although they have certain drawbacks. Upon comparing the different methods, it was found that near-infrared fluorescent probes are dominating the other detection methods.

CD44-Targeted Facile Enzymatic Activatable Chitosan Nanoparticles for Efficient Antitumor Therapy and Reversal of Multidrug Resistance

Nanoparticles are attractive platforms for the delivery of various anticancer therapeutics. Nevertheless, their applications are still limited by the relatively low drug loading capacity and the occurrence of multidrug resistance (MDR) against chemotherapeutics. In this study, we report that the integration of d-α-tocopherol succinate (VES) residue with both chitosan and paclitaxel (PTX) led to significant improvement of drug loading capacity and drug loading efficiency through the enhancement of drug/carrier interaction. After the incorporation of hyaluronic acid containing PEG side chains (HA-PEG), higher serum stability and more efficient cellular uptake were obtained. Due to HA coating, VES residues and the enzymatic responsive drug release property, such facile nanoparticles actively targeted cancer cells that overexpress CD44 receptor and efficiently reversed the MDR of treated cells, but caused no significant toxicity to mouse fibroblast (NIH-3T3). More importantly, with HA-PEG coating, longer blood circulation and more effective tumor accumulation were achieved for prodrug nanoparticles. Finally, superior anticancer activity and excellent safety profile was demonstrated by HA-PEG coated enzymatically activatable prodrug nanoparticles compared to commercially available Taxol formulation.

A double-headed cathepsin B inhibitor devoid of warhead

Most synthetic inhibitors of peptidases have been targeted to the active site for inhibiting catalysis through reversible competition with the substrate or by covalent modification of catalytic groups. Cathepsin B is unique among the cysteine peptidase for the presence of a flexible segment, known as the occluding loop, which can block the primed subsites of the substrate binding cleft. With the occluding loop in the open conformation cathepsin B acts as an endopeptidase, and it acts as an exopeptidase when the loop is closed. We have targeted the occluding loop of human cathepsin B at its surface, outside the catalytic center, using a high-throughput docking procedure. The aim was to identify inhibitors that would interact with the occluding loop thereby modulating enzyme activity without the help of chemical warheads against catalytic residues. From a large library of compounds, the in silico approach identified [2-[2-(2,4-dioxo-1,3-thiazolidin-3-yl)ethylamino]-2-oxoethyl] 2-(furan-2-carbonylamino) acetate, which fulfills the working hypothesis. This molecule possesses two distinct binding moieties and behaves as a reversible, double-headed competitive inhibitor of cathepsin B by excluding synthetic and protein substrates from the active center. The kinetic mechanism of inhibition suggests that the occluding loop is stabilized in its closed conformation, mainly by hydrogen bonds with the inhibitor, thus decreasing endoproteolytic activity of the enzyme. Furthermore, the dioxothiazolidine head of the compound sterically hinders binding of the C-terminal residue of substrates resulting in inhibition of the exopeptidase activity of cathepsin B in a physiopathologically relevant pH range.

Cysteine proteases as disease markers

This review comprises issues concerning cysteine cathepsins (CCs): human peptidases belonging to papain family (C1) of clan CA of cysteine proteases: cathepsins B, L, H, S, K, F, V, X, W, O and C. The involvement of these enzymes in physiological and pathological processes is described, especially with respect to their application as diagnostic and prognostic markers. They participate in precursor protein activation (including proenzymes and prohormones), MHC-II-mediated antigen presentation, bone remodeling, keratinocytes differentiation, hair follicle cycle, reproduction and apoptosis. Cysteine cathepsins upregulation has been demonstrated in many human tumors, including breast, lung, brain, gastrointestinal, head and neck cancer, and melanoma. Besides cancer diseases, they have been implied to participate in inflammatory diseases, such as inflammatory myopathies, rheumatoid arthritis, and periodontitis. Also, certain hereditary disorders are connected with mutations in CCs genes, what is observed in pycnodysostosis resulted from catK gene mutation and Papillon-Lefevre and Haim-Munk syndrome caused by catC gene defect. The potential application of cysteine cathepsins in diagnosis and/or prognosis is discussed in cancer diseases (breast, lung, head and neck, ovarian, gastrointestinal cancers, melanoma), as well as other disorders (periodontitis, rheumatoid arthritis, osteoarthritis).

CA-074, but not its methyl ester CA-074Me, is a selective inhibitor of cathepsin B within living cells

Studies using inhibitors that reportedly discriminate between cathepsin B and related lysosomal cysteine proteinases have implicated the enzyme in a wide range of physiological and pathological processes. The most popular substance to selectively inhibit cathepsin B in vivo is CA-074Me, the methyl ester of the E-64 derivative CA-074. However, we now have found that CA-074Me inactivates both cathepsin B and cathepsin L within murine fibroblasts. In contrast, exposure of these cells to the parental compound CA-074 leads to the selective inhibition of endogenous cathepsin B, while intracellular cathepsin L remains unaffected. These results indicate that CA-074 rather than CA-074Me should be used to specifically inactivate cathepsin B within living cells.

Membrane-anchored Cbl suppresses Hck protein-tyrosine kinase mediated cellular transformation

The mammalian proto-oncogene Cbl and its cellular homologues in Caenorhabditis elegans (Sli-1) and Drosophila (D-Cbl) are negative regulators of some growth factor receptor signaling pathways. Herein we show that Cbl can negatively regulate another signaling molecule, namely theSrc-family kinase Hck by targeting it for degradation. Hck-mediated cellular transformation of murine fibroblasts is reverted by ectopic expression of a membrane-anchored allele of Cbl as assessed by the cellular morphology, suppression of anchorage independent growth, and an overall reduction in the total tyrosine phosphorylation levels within the cells. The expression of Cbl at the plasma membrane targets both Hck and itself for ubiquitination and degradation, requiring an intact RING finger. Pharmacological inhibition of the proteasome prevents the degradation of Hck correlating with an increase in the phosphotyrosine levels within the cells. Activated Hck and membrane-anchored Cbl are present in similar subcellular localizations and co-immunoprecipitate, suggesting that their interaction is required for subsequent ubiquitination and degradation. Interestingly, both constitutively active and kinase-inactive Hck interact with and are targeted for degradation by Cbl. This work illustrates alternate means to regulate Src-family kinases, and suggests that Cbl may be able to suppress many signaling pathways that are activated in various proliferative syndromes including cancer.

Lysosomal multienzyme complex: biochemistry, genetics, and molecular pathophysiology

Lysosomal enzymes sialidase (alpha-neuraminidase), beta-galactosidase, and N-acetylaminogalacto-6-sulfate sulfatase are involved in the catabolism of glycolipids, glycoproteins, and oligosaccharides. Their functional activity in the cell depends on their association in a multienzyme complex with lysosomal carboxypeptidase, cathepsin A. We review the data suggesting that the integrity of the complex plays a crucial role at different stages of biogenesis of lysosomal enzymes, including intracellular sorting and proteolytic processing of their precursors. The complex plays a protective role for all components, extending their half-life in the lysosome from several hours to several days; and for sialidase, the association with cathepsin A is also necessary for the expression of enzymatic activity. The disintegration of the complex due to genetic mutations in its components results in their functional deficiency and causes severe metabolic disorders: sialidosis (mutations in sialidase), GM1-gangliosidosis and Morquio disease type B (mutations in beta-galactosidase), galactosialidosis (mutations in cathepsin A), and Morquio disease type A (mutations in N-acetylaminogalacto-6-sulfate sulfatase). The genetic, biochemical, and direct structural studies described here clarify the molecular pathogenic mechanisms of these disorders and suggest new diagnostic tools.

Pathologic gene expression in Gaucher disease: up-regulation of cysteine proteinases including osteoclastic cathepsin K

Deficiency of lysosomal acid β-glucosidase induces glycolipid storage in the macrophages of Gaucher disease but the pathways of multisystem tissue injury and destruction are unknown. To investigate the cognate molecular pathology of this inflammatory disorder, genes that were differentially expressed in spleen samples from a patient with Gaucher disease (Gaucher spleen) were isolated. Of 64 complementary DNA (cDNA) fragments sequenced from an enriched Gaucher cDNA library, 5 encode lysosomal proteins (cathepsins B, K, and S, α-fucosidase, and acid lipase), 10 encode other known proteins, and 2 represent novel sequences from human macrophage cell lines. Transcript abundance of the cathepsins, novel genes, pulmonary and activation-regulated chemokine (PARC), and NMB, a putative tumor suppressor gene, was greatly increased. Immunoblotting showed increased mature forms of all 3 cathepsins found in samples of Gaucher spleens. Immunofluorescence microscopy showed strong cathepsin B and K reactions in sinusoidal endothelium and Gaucher cells. The respective means, plus or minus SD, of cathepsin B, K, and S activities were 183 ± 35, 97 ± 39, and 91 ± 45 nmol/min/mg protein in 4 Gaucher spleens, and 26 ± 4, 10.5 ± 2, and 4.0 ± 2.1 nmol/min/mg protein in 3 control spleens. Plasma cathepsin B, K, and S activities were also elevated in Gaucher disease plasma (P < .001), but compared with control plasma samples, neither cathepsin B nor K activities were significantly elevated in 8 patients with nonglycosphingolipid lysosomal storage diseases or in 9 patients with other glycosphingolipidoses, which suggests disease specificity. All 3 cathepsin activities were increased 2-fold to 3-fold in Gaucher sera compared with control sera. In all 6 patients treated by enzyme replacement for 16-22 months, serum cathepsin activities decreased significantly (P < .01). Longitudinal studies confirmed the progressive reduction of proteinase activities during imiglucerase therapy but in 3 Gaucher patients with mild disease not so treated, serum cathepsin activities remained constant or increased during follow-up. Enhanced expression of cysteine proteinases may promote tissue destruction. Moreover, the first identification of aberrant cathepsin K expression in hematopoietic tissue other than osteoclasts implicates this protease in the breakdown of the matrix that characterizes lytic bone lesions in Gaucher disease.

Pathologic gene expression in Gaucher disease: up-regulation of cysteine proteinases including osteoclastic cathepsin K

Deficiency of lysosomal acid β-glucosidase induces glycolipid storage in the macrophages of Gaucher disease but the pathways of multisystem tissue injury and destruction are unknown. To investigate the cognate molecular pathology of this inflammatory disorder, genes that were differentially expressed in spleen samples from a patient with Gaucher disease (Gaucher spleen) were isolated. Of 64 complementary DNA (cDNA) fragments sequenced from an enriched Gaucher cDNA library, 5 encode lysosomal proteins (cathepsins B, K, and S, α-fucosidase, and acid lipase), 10 encode other known proteins, and 2 represent novel sequences from human macrophage cell lines. Transcript abundance of the cathepsins, novel genes, pulmonary and activation-regulated chemokine (PARC), and NMB, a putative tumor suppressor gene, was greatly increased. Immunoblotting showed increased mature forms of all 3 cathepsins found in samples of Gaucher spleens. Immunofluorescence microscopy showed strong cathepsin B and K reactions in sinusoidal endothelium and Gaucher cells. The respective means, plus or minus SD, of cathepsin B, K, and S activities were 183 ± 35, 97 ± 39, and 91 ± 45 nmol/min/mg protein in 4 Gaucher spleens, and 26 ± 4, 10.5 ± 2, and 4.0 ± 2.1 nmol/min/mg protein in 3 control spleens. Plasma cathepsin B, K, and S activities were also elevated in Gaucher disease plasma (P &lt; .001), but compared with control plasma samples, neither cathepsin B nor K activities were significantly elevated in 8 patients with nonglycosphingolipid lysosomal storage diseases or in 9 patients with other glycosphingolipidoses, which suggests disease specificity. All 3 cathepsin activities were increased 2-fold to 3-fold in Gaucher sera compared with control sera. In all 6 patients treated by enzyme replacement for 16-22 months, serum cathepsin activities decreased significantly (P &lt; .01). Longitudinal studies confirmed the progressive reduction of proteinase activities during imiglucerase therapy but in 3 Gaucher patients with mild disease not so treated, serum cathepsin activities remained constant or increased during follow-up. Enhanced expression of cysteine proteinases may promote tissue destruction. Moreover, the first identification of aberrant cathepsin K expression in hematopoietic tissue other than osteoclasts implicates this protease in the breakdown of the matrix that characterizes lytic bone lesions in Gaucher disease.

Molecular basis of GM1 gangliosidosis and Morquio disease, type B. Structure-function studies of lysosomal beta-galactosidase and the non-lysosomal beta-galactosidase-like protein

GM1 gangliosidosis and Morquio B disease are distinct disorders both clinically and biochemically yet they arise from the same beta-galactosidase enzyme deficiency. On the other hand, galactosialidosis and sialidosis share common clinical and biochemical features, yet they arise from two separate enzyme deficiencies, namely, protective protein/cathepsin A and neuraminidase, respectively. However distinct, in practice these disorders overlap both clinically and biochemically so that easy discrimination between them is sometimes difficult. The principle reason for this may be found in the fact that these three enzymes form a unique complex in lysosomes that is required for their stability and posttranslational processing. In this review, I focus mainly on the primary and secondary beta-galactosidase deficiency states and offer some hypotheses to account for differences between GM1 gangliosidosis and Morquio B disease.