A thiol proteinase inhibitor, E-64-d, corrects the abnormalities in concanavalin A cap formation and the lysosomal enzyme activity in leucocytes from patients with Chediak-Higashi syndrome by reversing the down-regulated protein kinase C activity

Effects of functionally diverse calpain system on immune cells

Calpains are a family of nonlysosomal cysteine proteases, which play important roles in numerous physiological and pathological processes. Locations of them dictates the functions so that they are classified as ubiquitously expressed calpains and tissue-specific calpains. Recent studies are mainly focused on conventional calpains (calpain-1,2) in development and diseases, and increasing people pay attention to other subtypes of calpains but may not been summarized appropriately. Growing evidence suggests that calpains are also involved in immune regulation. However, seldom articles review the regulation of calpains on immune cells. The aim of this article is to review the research progress of each calpain isozyme and the effect of calpains on immune cells, especially the promotion effect of calpains on the immune response of macrophage, neutrophils, dendritic cells, mast cells, natural killed cells, and lymphocytes. These effects would hold great promise for the clinical application of calpains as a practicable therapeutic option in the treatment of immune related diseases.

Platelets: still a therapeutical target for haemostatic disorders

Platelets are cytoplasmatic fragments from bone marrow megakaryocytes present in blood. In this work, we review the basis of platelet mechanisms, their participation in syndromes and in arterial thrombosis, and their potential as a target for designing new antithrombotic agents. The option of new biotechnological sources is also explored.

Enhanced diacylglycerol production by phospholipase D activation is responsible for abnormal increase in concanavalin A cap formation in polymorphonuclear leukocytes from Chediak-Higashi syndrome (beige) mice

We previously reported that enhanced ceramide production induces calpain-mediated proteolysis of protein kinase C (PKC) in leukocytes from Chediak-Higashi syndrome (CHS). In the present study, we demonstrated that phospholipase D (PLD) inhibitors ameliorated abnormal increases in concanavalin A (Con A) cap formation in polymorphonuclear leukocytes (PMNs) from beige mouse, an animal model of CHS. PLD activity in PMNs from beige mice enhanced at 30 to 60s after Con A stimulation. In Con A-stimulated beige PMNs, both neutral sphingomyelinase (N-SMase) and acidic sphingomyelinase (A-SMase) activities enhanced, and ceramide levels are also increased. We found that ceramide levels were reversed by the treatment of beige PMNs with propranolol which inhibits phosphatidic acid phosphohydrolase. In addition, we showed that diacylgycerol (DAG) analogs enhance both N-SMase and A-SMase activities in PMNs from normal mice. We subsequently examined the association of CHS1 with PLD, and showed that expression of a truncated mutant of CHS1 in 293T cells induced abnormally rapid activation of PLD after phorbol ester stimulation. Moreover, we showed that specific inhibitors of 14-3-3 proteins, which interact with CHS1/LYST and bind PKC, did not affect abnormal increases in Con A cap formation in beige PMNs. These results suggest that the enhanced DAG production via the PLD pathway is associated with abnormal increases in Con A cap formation in beige PMNs, and that CHS1 may be involved in the regulation of PLD activity.

Involvement of diacylglycerol produced by phospholipase D activation in Aβ-induced reduction of sAPPα secretion in SH-SY5Y neuroblastoma cells

We previously reported that the thiol proteinase inhibitor, E-64-d, ameliorated amyloid β (Aβ)-induced reduction of soluble amyloid precursor protein α (sAPPα) secretion by reversing ceramide-induced protein kinase C down-regulation in SH-SY5Y neuroblastoma cells. In the present study, we showed that Aβ (1-42) peptide enhanced diacylglycerol (DAG) production by phospholipase D (PLD) activation in these cells. We subsequently examined whether PLD was involved in Aβ-induced reduction of sAPPα secretion and showed that 2 μM CAY10593, which selectively inhibits PLD2, ameliorated reduction of sAPPα secretion, whereas 50 nM CAY10593, which selectively inhibits PLD1, did not. Moreover, 50 µM propranolol, a phosphatidic acid phosphohydrolase inhibitor, also ameliorated Aβ-induced reduction of sAPPα secretion, suggesting that DAG may be responsible for Aβ-induced reduction of sAPPα. We subsequently examined whether DAG affects sAPPα secretion and showed that a DAG analog reduced sAPPα secretion in SH-SY5Y cells. In addition, DAG enhanced ceramide production by stimulating neutral sphingomyelinase (N-SMase) activity. We previously demonstrated that Aβ stimulates N-SMase activity in SH-SY5Y cells. Here, we showed that inhibition of PLD2 by 2 μM CAY10593 suppressed Aβ-induced N-SMase activation. Taken together, the results suggest that DAG produced through the PLD pathway is involved in Aβ-induced reduction of sAPPα secretion in SH-SY5Y cells.

The thiol proteinase inhibitor E-64-d ameliorates amyloid-β-induced reduction of sAPPα secretion by reversing ceramide-induced protein kinase C down-regulation in SH-SY5Y neuroblastoma cells

In Alzheimer's disease (AD), enhancing α-secretase processing of amyloid precursor protein (APP) is an important pathway to decrease neurotoxic amyloid β (Aβ) secretion. The α-secretase is reported to be regulated by protein kinase C (PKC) and various endogenous proteins or cell surface receptors. In this report, we first examined whether Aβ reduces α-secretase activity, and showed that Aβ peptide 1-40 (0.001 and 0.01 μM) reduced the secretion of soluble amyloid precursor protein α (sAPPα) in carbachol-stimulated SH-SY5Y neuroblastoma cells. E-64-d (3 μM), which is a potent calpain inhibitor that prevents PKC degradation, ameliorated the Aβ-induced reduction of sAPPα secretion. In addition, we observed that Aβ significantly enhanced ceramide production by activating neutral sphingomyelinase. The cell-permeable ceramide analog, C2-ceramide (1 μg/mL), also reduced sAPPα secretion, and in addition, E-64-d eliminated the observed decrease of sAPPα secretion. C2-ceramide induced down-regulation of PKC-α, -β1, and -β2 isozymes in SH-SY5Y cells. These findings suggest that ceramide may play an important role in sAPPα processing by modulating PKC activity.

The enlarged lysosomes in beige j cells result from decreased lysosome fission and not increased lysosome fusion

Chediak-Higashi syndrome is an autosomal recessive disorder that affects vesicle morphology. The Chs1/Lyst protein is a member of the BEige And CHediak family of proteins. The absence of Chs1/Lyst gives rise to enlarged lysosomes. Lysosome size is regulated by a balance between vesicle fusion and fission and can be reversibly altered by acidifying the cytoplasm using Acetate Ringer's or by incubating with the drug vacuolin-1. We took advantage of these procedures to determine rates of lysosome fusion and fission in the presence or absence of Chs1/Lyst. Here, we show by microscopy, flow cytometry and in vitro fusion that the absence of the Chs1/Lyst protein does not increase the rate of lysosome fusion. Rather, our data indicate that loss of this protein decreases the rate of lysosome fission. We further show that overexpression of the Chs1/Lyst protein gives rise to a faster rate of lysosome fission. These results indicate that Chs1/Lyst regulates lysosome size by affecting fission.

Novel Heterogenous CHS1 Mutations Identified in Five Japanese Patients with Chediak-Higashi Syndrome

Chediak-Higashi syndrome (CHS) is a rare, autosomal recessive disorder characterized by oculocutaneous albinism, recurrent bacterial infections and progressive neurological dysfunction. We demonstrate novel heterogenous mutations of CHS1, the responsive gene of CHS, identified in five Japanese patients with CHS. Patients 1, 2, and 3 were siblings, and they had albinism of the skin and hair. They all had a heterogenous two-base deletion (c.5541-5542 del AA, p.Q1847fsX1850) in exon 18. Patient 4 had a heterogenous single-base insertion (c.3944-3945 ins C, p.T1315fsX1331) in exon 10. The patient exhibited severe early-onset phenotype and suffered from hemophagocytic lymphohistiocytosis. Patient 5 had two heterogenous nonsense mutations; c.7982C>G, p.S2661X in exon 30 and c.8281A>T, p.R2761X in exon 31. The patient suffered from infections in childhood and had visual disturbance and albinism of the skin and hair. The CHS1 mutations described here have not been reported previously.

Effect of a thiol proteinase inhibitor, E-64-d, on susceptibility to infection with Staphylococcus aureus in Chediak–Higashi syndrome (beige) mice

We previously reported that abnormally down-regulated protein kinase C (PKC) activity is responsible for the impaired cellular function of natural killer cells and polymorphonuclear cells (PMNs), and the giant granule formation in fibroblasts in the beige mouse, an animal model of Chediak-Higashi syndrome. Here, we examine the effect of oral or intraperitoneal administration of E-64-d, which protects PKC from calpain-mediated proteolysis, on the impaired cellular function in PMNs from beige mice. We found that oral administration of E-64-d (12.5 mg/kg body weight per day) for three consecutive days, significantly improved the abnormally increased concanavalin A (Con A) cap formation and the decreased lysosomal enzyme activity in beige PMNs. In addition, E-64-d significantly improved the delayed bactericidal activity against Staphylococcus aureus. In contrast, E-64-d at the same dose did not affect these cellular functions in PMNs from C57BL/6J mice. We confirmed that the abnormal down-regulation of PKC after Con A stimulation was eliminated in PMNs from E-64-d-treated beige PMNs. We then examined whether the administration of E-64-d to beige mice improved the susceptibility to experimental infection with S. aureus (2x10(8)/mouse). Both intraperitoneal and oral administration of E-64-d to beige mice resulted in a significant increase in survival, whereas E-64-d at the same dose did not alter the survival rate in normal mice. These results suggest that the administration of E-64-d may be effective against severe bacterial infection in Chediak-Higashi syndrome.

Neutrophil elastase depends on serglycin proteoglycan for localization in granules

Granule proteins play a major role in bacterial killing by neutrophils. Serglycin proteoglycan, the major intracellular proteoglycan of hematopoietic cells, has been proposed to play a role in sorting and packing of granule proteins. We examined the content of major neutrophil granule proteins in serglycin knockout mice and found neutrophil elastase absent from mature neutrophils as shown by activity assay, Western blotting, and immunocytochemistry, whereas neutrophil elastase mRNA was present. The localization of other neutrophil granule proteins did not differ between wild-type and serglycin knockout mice. Differential counts and neutrophil ultrastructure were unaffected by the lack of serglycin, indicating that defective localization of neutrophil elastase does not induce neutropenia itself, albeit mutations in the neutrophil elastase gene can cause severe congenital neutropenia or cyclic neutropenia. The virulence of intraperitoneally injected Gram-negative bacteria (Klebsiella pneumoniae) was increased in serglycin knockout mice compared with wild-type mice, as previously reported for neutrophil elastase knockout mice. Thus, serglycin proteoglycan has an important role in localizing neutrophil elastase in azurophil granules of neutrophils, while localization of other granule proteins must be mediated by other mechanisms.

Use of expression constructs to dissect the functional domains of the CHS/beige protein: identification of multiple phenotypes

The Chediak-Higashi Syndrome (CHS) and the orthologous murine disorder beige are characterized at the cellular level by the presence of giant lysosomes. The CHS1/Beige protein is a 3787 amino acid protein of unknown function. To determine functional domains of the CHS1/Beige protein, we generated truncated constructs of the gene/protein. These truncated proteins were transiently expressed in Cos-7 or HeLa cells and their effect on membrane trafficking was examined. Beige is apparently a cytosolic protein, as are most transiently expressed truncated Beige constructs. Expression of the Beige construct FM (amino acids 1-2037) in wild-type cells led to enlarged lysosomes. Similarly, expression of a 5.5-kb region (amino acids 2035-3787) of the carboxyl terminal of Beige (22B) also resulted in enlarged lysosomes. Expression of FM solely affected lysosome size, whereas expression of 22B led to alterations in lysosome size, changes in the Golgi and eventually cell death. The two constructs could be used to further dissect phenotypes resulting from loss of the Beige protein. CHS or beigej fibroblasts show an absence of nuclear staining using a monoclonal antibody directed against phosphatidylinositol 4,5 bisphosphate [PtdIns(4,5) P2]. Transformation of beige j fibroblasts with a YAC containing the full-length Beige gene resulted in the normalization of lysosome size and nuclear PtdIns(4,5)P2 staining. Expression of the carboxyl dominant negative construct 22B led to loss of nuclear PtdIns(4,5)P2 staining. Expression of the FM dominant negative clone did not alter nuclear PtdIns(4,5) P2 localization. These results suggest that the Beige protein interacts with at least two different partners and that the Beige protein affects cellular events, such as nuclear PtdIns(4,5)P2 localization, in addition to lysosome size.

A model for PKC involvement in the pathogenesis of inborn errors of metabolism

A model for the possible involvement of Protein Kinase C (PKC) in the pathogenesis of inborn errors of metabolism has been proposed. According to this model, perturbation of PKC activity by the accumulation of naturally occurring compounds serves as a unifying functional link between genotype and phenotype. Recent reports regarding an increasing number of modulating metabolites, specific PKC-subtypes activities, their effect on transcription factors and gene expression in various diseases and additional PKC-substrates expand the model. A re-examination of the proposed model in view of these reports and, vice versa, a review of these reports in the context of the proposed model reveal some common phenotypic outcomes in inborn errors of fatty acid-, cholesterol- and homocystine-metabolism as well as lysosomal and peroxisomal diseases.

Chediak-Higashi Syndrome: a rare disorder of lysosomes and lysosome related organelles

Chediak-Higashi Syndrome (CHS) is a rare autosomal recessive disorder characterized by severe immunologic defects including recurrent bacterial infections, impaired chemotaxis and abnormal natural killer (NK) cell function. Patients with this syndrome exhibit other symptoms such as an associated lymphoproliferative syndrome, bleeding tendencies, partial albinism and peripheral neuropathies. The classic diagnostic feature of CHS is the presence of huge lysosomes and cytoplasmic granules within cells. Similar defects are found in other mammals, the most well studied being the beige mouse and Aleutian mink. A positional cloning approach resulted in the identification of the Beige gene on chromosome 13 in mice and the CHS1/LYST gene on chromosome 1 in humans. The protein encoded by this gene is 3801 amino acids and is highly conserved throughout evolution. The identification of CHS1/Beige has defined a family of genes containing a common BEACH motif. The function of these proteins in vesicular trafficking remains unknown.