Differential sensitivity of anti-IgM-induced and NaF-induced inositol phospholipid metabolism to serine protease inhibitors in BAL17 B lymphoma cells

A BAL17 B lymphoma cell line bearing mu and delta chains on its surface behaves in a similar manner to normal mature B cells in terms of initial biochemical transmembrane signalling [Mizuguchi, Beaven, Ohara & Paul (1986) J. Immunol. 137, 2162-2167; Mizuguchi, Yong-Yong, Nakabayashi, Huang, Beaven, Chused & Paul (1987) J. Immunol. 139, 1054-1059]. Therefore the effects of protease inhibitors on increases in inositol phospholipid metabolism and intracellular free calcium concentration ([Ca2+]i) were examined. We show that the serine protease inhibitors Tos-Phe-CH2Cl (1-chloro-4-phenyl-3-L-tosylamidobutan-2-one-, TPCK) and Tos-Lys-CH2Cl (7-amino-1-chloro-3-L-tosylamidoheptan-2-one; TLCK) inhibit anti-IgM-mediated accumulation of inositol phosphates in a dose-dependent manner. InsP3 production induced by anti-IgM is also inhibited by pretreatment with Tos-Lys-CH2Cl or Tos-Phe-CH2Cl. Tos-Lys-CH2Cl- Tos-Phe-CH2Cl-mediated inhibition is not overcome by high concentrations of anti-IgM. Moreover, anti-IgM-mediated increases in [Ca2+]i are inhibited by pretreatment of the cells with these inhibitors. However, increases in inositol phospholipid metabolism caused by NaF, an activator of guanine-nucleotide-binding proteins (G-proteins), are approx. 10-fold more resistant to Tos-Lys-CH2Cl and Tos-Phe-CH2Cl inhibition compared with anti-IgM-induced changes. Furthermore, NaF-induced increases in [Ca2+]i are not inhibited by Tos-Lys-CH2Cl or Tos-Phe-CH2Cl pretreatment, suggesting that the inhibitors act at a step proximal to phospholipase C activation. The Tos-Lys-CH2Cl or Tos-Phe-CH2Cl treatment does not change the membrane IgM density as measured by flow cytometry, indicating that the active site of the inhibitors is distal to the membrane IgM molecule. These results indicate that serine proteases may be involved in coupling the receptor cross-linkage to G-protein.

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Role of proteolysis in apoptosis: involvement of serine proteases in internucleosomal DNA fragmentation in immature thymocytes

Biochemistry and Cell Biology ◽

10.1139/o93-071 ◽

1993 ◽

Vol 71 (9-10) ◽

pp. 488-500 ◽

Cited By ~ 73

Author(s):

Valerie M. Weaver ◽

Boleslaw Lach ◽

P. Roy Walker ◽

Marianna Sikorska

Keyword(s):

Molecular Weight ◽

Serine Protease ◽

High Molecular Weight ◽

Protease Inhibitors ◽

Dna Fragmentation ◽

Dna Cleavage ◽

Apoptotic Cell ◽

Dependent Manner ◽

Serine Protease Inhibitors ◽

High Molecular Weight Dna

Three chemically distinct serine, but not cysteine, protease inhibitors (phenylmethylsulphonyl fluoride, N-tosyl-L-phenylalanylchloromethyl ketone and 3,4-dichloroisocoumarin) prevented, in a dose-dependent manner, the characteristic apoptotic internucleosomal DNA cleavage (DNA ladder) typically observed in thymocytes in response to dexamethasone and teniposide VM-26. This effect was not the result of a direct inhibition of the Ca2+, Mg2+-dependent endonuclease, since oligonucleosomal DNA cleavage occurred in the presence of these inhibitors in isolated nuclei. The proteolytic step occurred at a very early stage of apoptosis, and preincubation of thymocytes with the inhibitors before dexamethasone or teniposide VM-26 were added irreversibly suppressed ladder formation. This implied that the cellular effector(s) of these compounds preexisted and were not resynthesized in response to the inducers of apoptosis. Serine protease inhibitors also suppressed apoptotic cell shrinkage and complete nuclear collapse, suggesting that these morphological changes were directly related to internucleosomal fragmentation of DNA. However, the serine protease inhibitors did not prevent high molecular weight DNA cleavage (> 50 kilobases) that preceded the ladder formation and thymocytes still died by apoptosis. This supported the view that internucleosomal DNA cleavage, considered to be the biochemical marker of apoptosis, might in fact be a late and dispensable step and that the newly described high molecular weight DNA cleavage might be a better indicator of apoptosis.Key words: serine protease, apoptosis, internucleosomal DNA fragmentation, high molecular weight DNA cleavage, protease inhibitors.

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Serine Protease Inhibitors Block Invasion of Host Cells by Toxoplasma gondii

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.43.6.1358 ◽

1999 ◽

Vol 43 (6) ◽

pp. 1358-1361 ◽

Cited By ~ 65

Author(s):

V. Conseil ◽

M. Soête ◽

J. F. Dubremetz

Keyword(s):

Toxoplasma Gondii ◽

Serine Protease ◽

Protease Inhibitors ◽

Early Stage ◽

Protozoan Parasite ◽

Gliding Motility ◽

Host Cells ◽

Dependent Manner ◽

Serine Protease Inhibitors ◽

Experimental Conditions

ABSTRACT We investigated the effect of protease inhibitors on the asexual development of the protozoan parasite Toxoplasma gondii. Among the inhibitors tested only two irreversible serine protease inhibitors, 3,4-dichloroisocoumarin and 4-(2-aminoethyl)-benzenesulfonyl fluoride, clearly prevented invasion of the host cells by specifically affecting parasite targets in a dose-dependent manner, with 50% inhibitory concentrations between 1 and 5 and 50 and 100 μM, respectively. Neither compound significantly affected parasite morphology, basic metabolism, or gliding motility within the range of the experimental conditions in which inhibition of invasion was demonstrated. No partial invasion was observed, meaning that inhibition occurred at an early stage of the interaction. These results suggest that at least one serine protease of the parasite is involved in the invasive process of T. gondii.

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