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Glucose deprivation activates a cAMP-independent protein kinase from Trypanosoma equiperdum. Parasitology 2018; 146:643-652. [PMID: 30419978 DOI: 10.1017/s0031182018001920] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Kemptide (sequence: LRRASLG) is a synthetic peptide holding the consensus recognition site for the catalytic subunit of the cAMP-dependent protein kinase (PKA). cAMP-independent protein kinases that phosphorylate kemptide were stimulated in Trypanosoma equiperdum following glucose deprivation. An enriched kemptide kinase-containing fraction was isolated from glucose-starved parasites using sedimentation throughout a sucrose gradient, followed by sequential chromatography on diethylaminoethyl-Sepharose and Sephacryl S-300. The trypanosome protein possesses a molecular mass of 39.07-51.73 kDa, a Stokes radius of 27.4 Ǻ, a sedimentation coefficient of 4.06 S and a globular shape with a frictional ratio f/fo = 1.22-1.25. Optimal enzymatic activity was achieved at 37 °C and pH 8.0, and kinetic studies showed Km values for ATP and kemptide of 11.8 ± 4.1 and 24.7 ± 3.8 µm, respectively. The parasite enzyme uses ATP and Mg2+ and was inhibited by other nucleotides and/or analogues of ATP, such as cAMP, AMP, ADP, GMP, GDP, GTP, CTP, β,γ-imidoadenosine 5'-triphosphate and 5'-[p-(fluorosulfonyl)benzoyl] adenosine, and by other divalent cations, such as Zn2+, Mn2+, Co2+, Cu2+, Ca2+ and Fe2+. Additionally, the trypanosome kinase was inhibited by the PKA-specific heat-stable peptide inhibitor PKI-α. This study is the first biochemical and enzymatic characterization of a protein kinase from T. equiperdum.
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Tagoe DNA, Kalejaiye TD, de Koning HP. The ever unfolding story of cAMP signaling in trypanosomatids: vive la difference! Front Pharmacol 2015; 6:185. [PMID: 26441645 PMCID: PMC4561360 DOI: 10.3389/fphar.2015.00185] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2015] [Accepted: 08/17/2015] [Indexed: 12/25/2022] Open
Abstract
Kinetoplastids are unicellular, eukaryotic, flagellated protozoans containing the eponymous kinetoplast. Within this order, the family of trypanosomatids are responsible for some of the most serious human diseases, including Chagas disease (Trypanosoma cruzi), sleeping sickness (Trypanosoma brucei spp.), and leishmaniasis (Leishmania spp). Although cAMP is produced during the life cycle stages of these parasites, its signaling pathways are very different from those of mammals. The absence of G-protein-coupled receptors, the presence of structurally different adenylyl cyclases, the paucity of known cAMP effector proteins and the stringent need for regulation of cAMP in the small kinetoplastid cells all suggest a significantly different biochemical pathway and likely cell biology. However, each of the main kinetoplastid parasites express four class 1-type cyclic nucleotide-specific phosphodiesterases (PDEA-D), which have highly similar catalytic domains to that of human PDEs. To date, only TbrPDEB, expressed as two slightly different isoforms TbrPDEB1 and B2, has been found to be essential when ablated. Although the genomes contain reasonably well conserved genes for catalytic and regulatory domains of protein kinase A, these have been shown to have varied structural and functional roles in the different species. Recent discovery of a role of cAMP/AMP metabolism in a quorum-sensing signaling pathway in T. brucei, and the identification of downstream cAMP Response Proteins (CARPs) whose expression levels correlate with sensitivity to PDE inhibitors, suggests a complex signaling cascade. The interplay between the roles of these novel CARPs and the quorum-sensing signaling pathway on cell division and differentiation makes for intriguing cell biology and a new paradigm in cAMP signal transduction, as well as potential targets for trypanosomatid-specific cAMP pathway-based therapeutics.
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Affiliation(s)
- Daniel N A Tagoe
- Wellcome Trust Centre for Molecular Parasitology, University of Glasgow , Glasgow, UK ; Institute of Infection, Inflammation and Immunity, College of Medical, Veterinary and Life Sciences, University of Glasgow , Glasgow, UK ; Department of Laboratory Technology, Division of Medical Laboratory Technology, University of Cape Coast , Cape Coast, Ghana
| | - Titilola D Kalejaiye
- Institute of Infection, Inflammation and Immunity, College of Medical, Veterinary and Life Sciences, University of Glasgow , Glasgow, UK
| | - Harry P de Koning
- Institute of Infection, Inflammation and Immunity, College of Medical, Veterinary and Life Sciences, University of Glasgow , Glasgow, UK
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3
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Vij A, Biswas A, Bhattacharya A, Das PK. A soluble phosphodiesterase in Leishmania donovani negatively regulates cAMP signaling by inhibiting protein kinase A through a two way process involving catalytic as well as non-catalytic sites. Int J Biochem Cell Biol 2014; 57:197-206. [PMID: 25310904 DOI: 10.1016/j.biocel.2014.10.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2014] [Revised: 09/09/2014] [Accepted: 10/02/2014] [Indexed: 10/24/2022]
Abstract
Intracellular cAMP level and cAMP mediated responses are elevated when Leishmania are exposed to macrophage phagolysosome conditions (37 °C and pH 5.5). Phosphodiesterases play major role in cAMP regulation and in the present study we have cloned and characterized a 2.1 kb cytosolic isoform of phosphodiesterase from Leishmania donovani (LdPDED) which plays important role in cAMP homeostasis when the promastigotes are exposed to macrophage phagolysome conditions for converting to axenic amastigotes. Domain characterization suggested the presence of two pseudo-substrate sites similar to the ones present in the regulatory subunit of cAMP-dependent protein kinase A (PKA) and a putative PKA phosphorylation site at T(708) of C-terminus of LdPDED. Deletion constructs and site directed mutagenesis revealed the ability of LdPDED to interact with L. donovani PKA catalytic subunits (LdPKAC1 and LdPKAC2) resulting in inhibition of kinase activity in one hand and increase of phosphodiesterase activity through PKA mediated phosphorylation at putative phosphorylation site on the other hand. This study therefore identifies a unique phosphodiesterase in L. donovani which appears to regulate cAMP-dependent PKA signaling through a two way process.
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Affiliation(s)
- Amit Vij
- Infectious Diseases and Immunology Division, CSIR-Indian Institute of Chemical Biology, Kolkata, India
| | - Arunima Biswas
- Infectious Diseases and Immunology Division, CSIR-Indian Institute of Chemical Biology, Kolkata, India
| | | | - Pijush K Das
- Infectious Diseases and Immunology Division, CSIR-Indian Institute of Chemical Biology, Kolkata, India.
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4
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Abstract
Compared with the impressive progress in understanding signal transduction pathways and mechanisms in mammalian systems, advances in protozoan signalling processes, including cyclic nucleotide metabolism, have been very slow. This is in large part connected to the fact that the components of these pathways are very different in the protozoan parasites, as confirmed by the recently completed genome. For instance, kinetoplastids have no equivalents to the mammalian Class I adenylyl cyclases (ACs) in their genomes nor any of the subunits of the associated G-proteins. The cyclases in kinetoplastid parasites contain a single transmembrane domain, a conserved intracellular catalytic domain and a highly variable extracellular domain - consistent with the expression of multiple receptor-activated cyclases - but no receptor ligands, agonists or antagonists have been identified. Apicomplexan AC and guanylyl cyclase (GC) are even more unusual, potentially being bifunctional, harbouring either a putative ion channel (AC) or a P-type ATPase-like domain (GC) alongside the catalytic region. Phosphodiesterases (PDEs) and cyclic-nucleotide-activated protein kinases are essentially conserved in protozoa, although mostly insensitive to inhibitors of the mammalian proteins. Some of the PDEs have now been validated as promising drug targets. In the following manuscript, we will summarize the existing literature on cAMP and cGMP in protozoa: cyclases, PDEs and cyclic-nucleotide-dependent kinases.
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Affiliation(s)
- Matthew K Gould
- Biomedical Research Centre, Institute of Infection, Immunity & Inflammation, College of Medical, Veterinary & Life Sciences, University of Glasgow, Glasgow, UK
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Alvarez-Rueda N, Biron M, Le Pape P. Infectivity of Leishmania mexicana is associated with differential expression of protein kinase C-like triggered during a cell-cell contact. PLoS One 2009; 4:e7581. [PMID: 19851504 PMCID: PMC2762032 DOI: 10.1371/journal.pone.0007581] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2009] [Accepted: 10/04/2009] [Indexed: 01/07/2023] Open
Abstract
Mammalian host cell invasion by Leishmania is a complex process in which various parasite and host cell components interact, triggering the activation of signaling cascades in both cells. Little is known regarding PKC biological functions in Leishmania sp. during parasite-macrophage interaction. PKC-like enzyme was first identified in homogenates and membrane fraction of L. mexicana stationary promastigotes by immunoblot. PKC-like enzyme activity was then detected in cell homogenates but also on intact promastigotes showing for the first time the presence of an ecto-PKC dependent on Ca2+/phosphatidylserine for activation. This ecto-PKC was activated with phorbol myristate acetate (PMA) and inhibited by RO-32-0432, a selective PKCαβIε bisindolylmaleimide inhibitor. Interestingly, the Leishmania PKC- activity was higher in the infective stationary than in non-infective logarithmic stage. Then, promastigotes at different stages of time proliferation curve were used in order to identify the role of PKC-like during macrophage invasion. After attachment to macrophages, PKC-like is over-expressed in promastigotes at the 6th culture day but also at the 4th day of culture corresponding to the maximal infection capacity. An antibody microarray for MAPK and PKC corroborate the Leishmania PKC-like over-expression during contact with macrophages. Pretreatment with RO-32-0432 inhibitor reduced the number of infected macrophages and the parasite burden. These data suggest for the first time a direct link between PKC expression level and infectivity, and provide evidence that PKC-like plays a critical role in attachment and in the internalization steps involved in the invasion process.
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Affiliation(s)
- Nidia Alvarez-Rueda
- Département de Parasitologie et de Mycologie Médicale, Université de Nantes, Nantes Atlantique Universités, EA 1155 - IICiMed, Faculté de Pharmacie, Nantes, France
| | - Marlène Biron
- Département de Parasitologie et de Mycologie Médicale, Université de Nantes, Nantes Atlantique Universités, EA 1155 - IICiMed, Faculté de Pharmacie, Nantes, France
| | - Patrice Le Pape
- Département de Parasitologie et de Mycologie Médicale, Université de Nantes, Nantes Atlantique Universités, EA 1155 - IICiMed, Faculté de Pharmacie, Nantes, France
- Laboratoire de Parasitologie-Mycologie, CHU de Nantes, Nantes, France
- * E-mail:
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Malki-Feldman L, Jaffe CL. Leishmania major: Effect of protein kinase A and phosphodiesterase activity on infectivity and proliferation of promastigotes. Exp Parasitol 2009; 123:39-44. [DOI: 10.1016/j.exppara.2009.05.010] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2009] [Revised: 04/30/2009] [Accepted: 05/13/2009] [Indexed: 10/20/2022]
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Siman-Tov MM, Ivens AC, Jaffe CL. Molecular cloning and characterization of two new isoforms of the protein kinase A catalytic subunit from the human parasite Leishmania. Gene 2002; 288:65-75. [PMID: 12034495 DOI: 10.1016/s0378-1119(02)00403-1] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Leishmania are protozoan parasites that cause extensive morbidity and mortality in humans. Genes for two new isoforms of the protein kinase A catalytic subunit (PKAC) in Leishmania, Lmpkac2a and Lmpkac2b, were cloned and characterized. The predicted open reading frames for these isoforms are 93.4% identical over 338 amino acids (aa). The conserved PK catalytic cores (subdomains I-XI) are identical, while the carboxy-terminal extensions differ by only two aa. However, LmPKAC2 shares only 62% identity over the 255 aa catalytic core region with the previously described LmPKAC1 (c-lpk2). Unlike LmPKAC1, the location of the FXXF motif at the carboxy-terminus is conserved in both LmPKAC2 isoforms; however, the aa sequence, LXXF, in isoform-2a is unusual. The leishmanial isoforms can be distinguished by their NH(2)-terminal extensions, which show minimal similarity at the primary sequence level. Structural analysis of the three enzymes based on the crystal structure of mammalian PKAs predicts that both LmPKAC2 isoforms, unlike LmPKAC1, have identical alpha-helix structures in the NH(2)-terminal extension. Lmpkac2 genes are located on chromosome 35 just downstream from the leishmanial prp8 gene. This genomic organization is conserved in two species of Leishmania and Crithidia fasciculata and allowed for the partial analysis of Cfpkac2a. Phylogenetic analysis groups the two LmPKAC2 isoforms together and separately from LmPKAC1, which is more similar to the Euglena gracilis PKAC, EPK2. These findings provide the basis for additional studies on the role of the PKA family in parasite differentiation and virulence.
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Affiliation(s)
- Michal M Siman-Tov
- Department of Parasitology, Hebrew University - Hadassah Medical School, Jerusalem 91220, Israel
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Banerjee C, Sarkar D. The cAMP-binding proteins of Leishmania are not the regulatory subunits of cAMP-dependent protein kinase. Comp Biochem Physiol B Biochem Mol Biol 2001; 130:217-26. [PMID: 11544092 DOI: 10.1016/s1096-4959(01)00232-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The most commonly used method to determine the cAMP binding activity in cytosolic extracts of promastigotes of Leishmania spp. underestimated by approximately 11.5-fold the total amount of [(3)H]cAMP bound, when compared with results obtained by the modified Millipore filter technique. Three cAMP-binding proteins (BPI, BPII and BPIII) were partially purified and characterized. The native molecular masses of BPI, BPII and BPIII were estimated to be 105, 155 and 145 kDa, respectively. The binding of [(3)H]cAMP to these proteins was affected to different extents by several cAMP analogues. Antibodies directed against the types I and II regulatory subunits of PKA did not cross-react with the leishmanial extract. Photoaffinity labeling of the cytosolic extracts with 8-N(3)-[(32)P]cAMP specifically labeled a band of M(r) 116000 and a band of M(r) 80000 partially saturable by cAMP. From these results, it is concluded that the leishmanial cAMP-binding proteins appear to belong to a different class distinct from the regulatory subunits of cAMP-dependent protein kinases.
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Affiliation(s)
- C Banerjee
- Leishmania Division and Department of Cell Biology, Indian Institute of Chemical Biology, 4 Raja S.C. Mullick Road, Calcutta 700 032, India
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Salotra P, Ralhan R, Sreenivas G. Heat-stress induced modulation of protein phosphorylation in virulent promastigotes of Leishmania donovani. Int J Biochem Cell Biol 2000; 32:309-16. [PMID: 10716628 DOI: 10.1016/s1357-2725(99)00134-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
In parasites such as Leishmania, the study of molecular events induced in response to heat stress is of immense interest since temperature increase is an integral part of the life cycle. Protein phosphorylation is known to control major steps of proliferation and differentiation in eukaryotic cells. Studies on intracellular signaling systems in protozoa are relatively recent. We have examined the effect of heat shock on the protein phosphorylation status in promastigotes of Leishmania donovani. The patterns of total protein phosphorylation and specific phosphorylation at tyrosine residues were examined using [32P]-orthophosphate labelling of the parasites and immunoblotting with a monoclonal anti-phosphotyrosine antibody. The major proteins of L. donovani that were phosphorylated at 24 degrees C had apparent molecular weights of 110, 105, 66-68, 55, 36-40 and 20 kDa. Heat shock (from 24 to 37 degrees C) led to a significant decrease in phosphorylation of the majority of phosphoproteins in the virulent promastigotes. On the other hand, the avirulent promastigotes did not show any decrease in protein phosphorylation on exposure to heat stress. Predominant phosphorylation at tyrosine residues was detectable in proteins of putative size 105-110 kDa in both virulent and avirulent parasites. Heat shock led to a reduction in the level of phosphotyrosine in both these proteins in the case of virulent parasites, while no such reduction was detectable in avirulent parasites. Significant modifications in the phosphorylation status of proteins in response to heat stress including that of tyrosine containing proteins, observed exclusively in virulent parasites, suggest that modulation of protein phosphorylation/dephosphorylation may play a role in signal transduction pathways in the parasite upon heat shock encountered on entering the mammalian host.
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Affiliation(s)
- P Salotra
- Molecular Biology Laboratory, Institute of Pathology (ICMR), New Delhi, India.
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10
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Abstract
Curative interference with signal transduction pathways is a spectacularly successful concept in many domains of modern pharmacology; indeed, the 'wonder drug' Viagra is but a humble inhibitor of a cyclic GMP (cGMP)-specific phosphodiesterase and, thus, interferes with cGMP-signaling in a strategic organ. In fact, about half of the 100 most successful drugs currently on the market act through modulating cellular signal transduction. Despite these encouraging findings, signal transduction pathways as potential drug targets in trypanosomatids have remained largely unexplored. However, what little is known indicates that adenylyl cyclases of trypanosomatids, and probably other enzymes of the cyclic nucleotide signaling pathways, are significantly different from their mammalian counterparts. Here, Christina Naula and Thomas Seebeck summarize what is known about cAMP signal transduction in trypanosomatids.
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Affiliation(s)
- C Naula
- University of Bern, Institute of General Microbiology, Switzerland
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11
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Pascuccelli V, Labriola C, Téllez-Iñón MT, Parodi AJ. Molecular and biochemical characterization of a protein kinase B from Trypanosoma cruzi. Mol Biochem Parasitol 1999; 102:21-33. [PMID: 10477173 DOI: 10.1016/s0166-6851(99)00076-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
A Trypanosoma cruzi gene, PKB, coding for a putative protein kinase was cloned and sequenced. Analysis of the sequence showed that the encoded protein (called PKB) corresponds to a relatively novel subgroup of Ser/Thr protein kinases denominated protein kinases B (PKB), related to A and C protein kinases (RAC), or protein kinases of the transforming retrovirus AKT8 (Akt) in which the catalytic domains show similarity to corresponding domains of protein kinases A and protein kinases C. Unlike mammalian enzymes belonging to the same subgroup, PKB did not have a pleckstrin (PH)-homologous domain. PKB was expressed in Escherichia coli and the recombinant protein was found to be a Thr-specific protein kinase that required Mn2+ for activity and used ATP as phosphate donor (Km = 1.8 microM). Classical protein kinase A and protein kinase C modulators and inhibitors were found to have only marginal or no effect on PKB activity. Antisera raised against the recombinant protein recognized PKB in Western blotting analysis of cell extracts as a membrane bound protein. Evidence was obtained suggesting the presence of a Cys-linked acyl anchor. Northern and Western blotting analysis showed that PKB was constitutively expressed in the lag, exponential and stationary phases of T. cruzi epimastigote growth, as well as in the amastigote and metacyclic trypomastigote stages of differentiation. This is the first description of the existence of a protein kinase B in trypanosomatid protozoa.
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Affiliation(s)
- V Pascuccelli
- Instituto de Investigaciones Bioquímicas Fundación Campomar, Buenos Aires, Argentina
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12
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Gomes CM, Monteiro HP, Gidlund M, Corbett CE, Goto H. Insulin-like growth factor-I induces phosphorylation in Leishmania (Leishmania) mexicana promastigotes and amastigotes. J Eukaryot Microbiol 1998; 45:352-5. [PMID: 9627996 DOI: 10.1111/j.1550-7408.1998.tb04548.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Protein phosphorylation controls major steps of proliferation and differentiation in eukaryotic cells. However there are few studies done in protozoa particularly when being triggered by external stimuli. In this paper we have examined the tyrosine- and serine/threonine-phosphorylated proteins in both promastigote and amastigote-like forms of Leishmania (Leishmania) mexicana stimulated with insulin-like growth factor (IGF)-I. Stimulation with IGF-I induces major tyrosine phosphorylation of a 185-kDa protein in promastigotes and 60- and 40-kDa proteins in amastigotes. Analysis of total phosphorylation revealed additional sets of phosphorylated proteins: a 110-kDa protein band in promastigotes and two other proteins of 120 and 95 kDa in the amastigote-like forms. To further analyze the IGF-I-mediated response we compared it with the phosphorylation pattern obtained with a known inducer of protein kinase C, phorbol myristate acetate. This analysis showed overlapping phosphorylation of most of the proteins but mainly of the 185- and 110-kDa proteins in the promastigotes and the 95-, 60- and 40-kDa proteins in the amastigote-like forms. We thus conclude that there are phosphorylation-dependent pathways in Leishmania parasites induced by IGF-I that are stage-specific.
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Affiliation(s)
- C M Gomes
- Department of Pathology, Medical Faculty of University of São Paulo, Brazil
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13
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Rivero-Lezcano OM, Chicharro C, Rivas L. Acidic pH stress induces protein tyrosine phosphorylation in Leishmania pifanoi. Mol Biochem Parasitol 1997; 84:123-9. [PMID: 9041527 DOI: 10.1016/s0166-6851(96)02789-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
In order to determine whether in vitro Leishmania exposure to conditions comparable to those encountered inside the host cell would induce specific signals, we have studied tyrosine phosphorylation patterns in Leishmania pifanoi. Incubation of L. pifanoi at acidic pH resulted in the phosphorylation of several proteins including three of 27, 43 and 51 kDa, as well as the dephosphorylation of a 175 and a 39 kDa proteins in promastigotes recently transformed. In contrast, heat shock at 37 degrees C did not change the tyrosine phosphorylation pattern. Phosphorylation only occurs at pH 5.0 or lower and reached completion after 1 h. Changes returned to the initial conditions in 2 h after pH medium neutralization, indicating a reversible mechanism of phosphorylation.
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14
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Dunn PP, Bumstead JM, Tomley FM. Sequence, expression and localization of calmodulin-domain protein kinases in Eimeria tenella and Eimeria maxima. Parasitology 1996; 113 ( Pt 5):439-48. [PMID: 8893529 DOI: 10.1017/s0031182000081506] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
We have isolated and sequenced cDNA clones from Eimeria tenella and Eimeria maxima which encode proteins that share homology with a recently described family of calmodulin-domain protein kinases. The primary sequence data show that each of the protein kinases can be divided into 2 main functional domains-an amino-terminal catalytic domain typical of serine/threonine protein kinases and a carboxy-terminal domain homologous to calmodulin, which is capable of binding calcium ions at 4 'EF-hand' motifs. Expression of the E. tenella calmodulin-domain protein kinase (EtCDPK) increased towards the end of oocyst sporulation, as judged by Northern and Western blotting, and indirect immunofluorescent antibody labelling showed that within a few minutes of adding sporozoites to target host cells in in vitro culture EtCDPK was found to be specifically associated with a filament-like structure that converges at the apical end of the parasite. Once the parasite entered the host cell EtCDPK appeared to be left on the host cell membrane at the point of entry, indicating a brief yet specific role for this molecule in the invasion of host cells by E. tenella.
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Affiliation(s)
- P P Dunn
- Institute for Animal Health, Compton, Newbury, Berkshire, UK
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15
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Siman-Tov MM, Aly R, Shapira M, Jaffe CL. Cloning from Leishmania major of a developmentally regulated gene, c-lpk2, for the catalytic subunit of the cAMP-dependent protein kinase. Mol Biochem Parasitol 1996; 77:201-15. [PMID: 8813666 DOI: 10.1016/0166-6851(96)02601-1] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Protein kinases are important in the regulation of cellular processes including growth and differentiation. Using the polymerase chain reaction with oligonucleotide primers derived from conserved regions of cAMP-dependent protein kinases (PKAs), three different DNA fragments were amplified from leishmanial genomic DNA. One fragment was used to isolate a stage specific gene, c-lpk2, from a Leishmania major genomic library. This gene shows high homology to other eukaryotic PKAs, and the open reading frame encodes a 332 amino acid protein with a predicted molecular mass of 38.2 kDa. When aligned with other PKAs the leishmanial enzyme has a unique eight amino acid extension at the carboxy terminus. The c-lpk2 gene is present as a single copy in L. major, L. donovani and L. amazonensis. The 5'-flanking region contains a polypyrimidine rich tract upstream from the predicted ATG start codon. The gene is highly expressed in promastigotes and barely detectable in amastigotes of L. major. Temperature increase was shown to rapidly down-regulate c-lpk2 expression. Transfer of L. amazonensis promastigotes to 35 degrees C resulted in the rapid disappearance of c-lpk2 mRNA (> 70% in 1 h), while at 26 degrees C the mRNA was more stable. The strict temperature dependence of mRNA degradation rate suggests that PKA expression is regulated post-transcriptionally.
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Affiliation(s)
- M M Siman-Tov
- Department of Parasitology, Hebrew University-Hadassah Medical School, Jerusalem, Israel
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16
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Nandi S, Sarkar D. Partial purification and characterization of a soluble protein phosphatase from Leishmania donovani promastigotes. Mol Cell Biochem 1995; 148:191-8. [PMID: 8594423 DOI: 10.1007/bf00928156] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
A soluble protein phosphatase from the promastigote form of the parasitic protozoan Leishmania donovani was partially purified using Sephadex G-100, DEAE-cellulose and again Sephadex G-100 columns. The partially purified enzyme showed a native molecular weight of about 42,000 in both Sephadex G-100 and sucrose density gradient centrifugation. The sedimentation constant, stokes radius and frictional ratio were found to be 3.43S, 2.8 nm and 1.20 respectively. The enzyme preferentially utilized phosphohistone as the best exogenous substrate. Mg2+ ions were essential for enzyme activity; among other metal ions Mn2+ can replace Mg2+ to a certain extent whereas Ca2+, Co2+ and Zn2+ could not substitute for Mg2+. The pH optimum of the enzyme was 6.5-7.5 and the temperature optimum 37 degrees C. The apparent Km for phosphohistone was 7.14 microM. ATP, ADP, inorganic phosphate and pyrophosphate had inhibitory effect on the enzyme activity whereas no inhibition was observed with sodium tartrate and okadaic acid. These results suggest that L. donovani promastigotes possess a protein phosphatase which has similar characteristics with the mammalian protein phosphatase 2C.
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Affiliation(s)
- S Nandi
- Department of Cell Biology, Indian Institute of Chemical Biology, Calcutta, India
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17
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Assefa D, Worku Y, Skoglund G. Protein kinase activities in Leishmania aethiopica: control by growth, transformation and inhibitors. BIOCHIMICA ET BIOPHYSICA ACTA 1995; 1270:157-62. [PMID: 7727538 DOI: 10.1016/0925-4439(94)00080-a] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Promastigotes of L. aethiopica express an ectokinase activity preferring histone V-S as substrate. A soluble kinase activity utilizing protamine and histone V-S, as well as a particulate fraction associated kinase activity preferring protamine are also expressed. The soluble histone kinase activity, but not the ectokinase, was expressed at a higher level in cells from late phases of growth, as compared to early log phase cultures. Transformation of L. aethiopica to an amastigote-like stage, resulted in almost complete loss of the kinase activities, with retained viability of the cells. Formycin-ATP only weakly inhibited the kinases while effectively inhibiting cell growth and thymidine incorporation. Staurosporin efficiently blocked the kinase activities and cell growth without affecting thymidine incorporation.
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Affiliation(s)
- D Assefa
- Department of Biochemistry, Addis Ababa University, Faculty of Medicine, Ethiopia
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Dell KR, Engel JN. Stage-specific regulation of protein phosphorylation in Leishmania major. Mol Biochem Parasitol 1994; 64:283-92. [PMID: 7935606 DOI: 10.1016/0166-6851(94)00030-1] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
We investigated whether there are changes in protein phosphorylation or protein kinase activities during the life cycle of Leishmania major. Using a kinase renaturation assay, we detected several leishmanial kinases at each stage of the life cycle. In particular we identified a 50-kDa kinase that is active in procyclic and metacyclic parasites but is inactive in amastigotes. An in vitro phosphorylation assay demonstrated that the pattern of serine and threonine phosphorylated proteins was regulated during the leishmanial life cycle; specifically changes in the phosphorylation of a 108-, a 62-, a 52- and a 49-kDa protein were detected. We present evidence that suggests that changes in phosphorylation of the 108-, 62- and 52-kDa proteins are due to the activity of one or more amastigote specific phosphatases. No differences were detectable in the relative ratios of phosphorylation on serine, threonine, and tyrosine residues in lysates from the different stages. In addition, the pattern of tyrosine phosphorylated proteins in lysates from different L. major developmental stages was similar as detected with a commercial antibody to phosphotyrosine. A 37-kDa phosphorylated protein reacted strongly with the antibody and comigrated with a 37-kDa protein identified in the in vitro phosphorylation assay. Our results support the hypothesis that protein phosphorylation plays an important role in signal transduction pathways in Leishmania major.
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Affiliation(s)
- K R Dell
- Department of Medicine, University of California, San Francisco 94143
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