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Adenylate-cyclase toxin of Bordetella pertussis as a marker for the study of the complement receptor CD11b/CD18 endocytosis.
Chvojková, Věra ; Bumba, Ladislav (advisor) ; Černý, Jan (referee)
Bordetella pertussis is an important human pathogen that causes an infection disease called whooping cough. This gram-negative bacterium produces an adenylate cyclase toxin (CyaA) that recognizes an integrin receptor CD11b/CD18 present on the surface of myeloid phagocytes and delivers an adenylate cyclase (AC) domain into the cell cytosol. This thesis deals with the endocytic machinery of CyaA and its potential use as a specific marker for endocytosis of the CD11b/CD18 receptor molecule. Detoxified mutant of CyaA, CyaA-AC- , that has the capacity to promote calcium influx as well the potassium efflux, was shown to trigger activation of the integrin receptor CD11b/CD18 followed with endocytic uptake by clathrin-dependent pathway. On the other side, the inactive mutant CyaA-KP-AC- that is unable to provoke integrin activation was endocytosed by clathrin-independent pathway. These results suggest that the various endocytic pathways of the CD11b/CD18 are determined by different conformational states of the receptor molecule.
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Assessing biochemical properties of PDE8A1: Design of experimental system in living cells"
Galica, Tomáš ; Černý, Jan (advisor) ; Mašek, Tomáš (referee)
4 Abstract Phosphodiesterases (PDEs), enzymes that hydrolyze cyclic nucleotides, are important components of signal transduction pathways in eukaryotic cells. Second messenger 3'-5'- cyclic adenosine monophosphate (cAMP) is hydrolyzed by specific PDEs. By controlling concentration levels of cAMP in cell, PDEs preserve favorable environment for successful transmission of the cAMP signal. Moreover, PDEs are activated by protein kinase A (PKA) in response to elevated cAMP concentration, which is a feature crucial for signal termination. PDE8A1 is a high-affinity cAMP-specific IBMX insensitive phosphodiesterase, an enzyme important for cAMP signaling. However, mostly due to a lack of specific inhibitor, its role has not been assessed in detail. This thesis reports cloning of PDE8A1, identification of its posttranslational modifications and subcellular localization, as well as an alternative approach to address PDE biology by the use of cyclase toxin from Bordetella pertussis. Keywords: phosphodiesterase, cAMP, posttranslational modification, myristoylation, palmitoylation, adenylate cyclase toxin
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Signalization of adenylate cyclase toxin of Bordetella pertussis in macrophages.
Černý, Ondřej ; Kuthan, Martin (referee) ; Kamanová, Jana (advisor)
Adenylate cyclase toxin (CyaA) is a key virulence factor of Bordetella pertussis, the causative agent of whooping cough. The toxin targets primarily myeloid phagocytes expressing CD11b/CD18 (αMβ2, CR3, Mac-1) and by elevation of cytosolic cAMP levels it paralyses their macropinocytic and opsono-phagocytic functions. Here, we dissected the cAMP-regulated pathway responsible for the block of macrophage macropinocytosis and characterized the capacity of CyaA-treated macrophages to shut- down Akt (protein kinase B, PKB) signaling; that controls nitric oxide (NO) production by macrophages. By using specific activators of protein kinase A (PKA) and for the exchange protein activated by cAMP (Epac), we show that activation of the cAMP effector Epac inhibits macropinocytosis in macrophages. Moreover, upon transfection of macrophages by the constitutively active and dominant negative variants of a downstream effector of Epac, the small GTPase Rap1, inhibition or upregulation of macrophage macropinocytosis was observed, respectively. It was reported previously that the Epac/Rap1 pathway regulates activity of tyrosin phosphatase SHP-1 as well as of protein phosphatase 2 A (PP2A). We show that inhibition of both tyrosin phosphatases and PP2A interferes with CyaA-mediated block of macropinocytosis. These...
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