Activation of MAPK kinase pathway by Gal/GalNAc adherence lectin of E. histolytica: gateway to host response.
Amoebiasis caused by the protozoan parasite Entamoeba histolytica is one of the leading parasitic causes of morbidity and mortality in the developing countries. Among the variety of virulence factors, an adherence lectin (Gal/GalNAc, 260 kDa) has been known to mediate colonization and subsequent host responses. It is a major cell surface antigen which is universally recognized by the immune sera of patients with amoebic liver abscess (ALA). The role of this lectin in cytolysis and phagocytosis of human colonic mucin glycoproteins has also been established. The objective of the present study was to elucidate the signal transduction events induced in response to Entamoeba histolytica derived Gal/GalNAc lectin in the target epithelial cells. We have attempted to define a pathway in target cells that could link this immunodominant antigen to a known biological pathway for target cell activation and triggering of subsequent disease pathology/parasite survival. Lectin stimulated cells showed immediate rise in (Ca2+)i concentration corresponding to 1517.31+/-16.3 nM (approximately) at 0-2 min. The intracellular calcium also extruded from the cells as was measured by increase in calcium green-1 fluorescence. Expression of several protein kinases was checked by western blotting to delineate the signaling pathway. Results showed that the expression of PLA2, PI3K, Ras p21, Ras GAP, ERK-MAPK, p38MAPK and PKC was significantly increased. Expression of Raf-1 and MEK-1 was also found to be significant, as determined by intensity analysis. Overall, it indicated activation of MAPKinase pathway which is implicated in a variety of cellular functions. On the basis of our observations it can be stated that there is a calcium mediated activation of PKC in target cells, by lectin, which inturn activates cyclic nucleotides and other protein kinases. These protein kinases further phosphorylated downstream signals in a sequential manner, thus leading to the activation of MAPKinase cascade. Activation of MAPK cascade, in our studies, is implicated in a variety of physiological cellular functions including apoptosis, proliferation, cytoskeleton rearrangements and permeability changes. However, future screening of the genes responsible for the transcription and translation of new proteins and their biological functions in response to lectin stimulation will prove useful in understanding this host-parasite relationship.
Rawal
Seema
S
Department of Experimental Medicine and Biotechnology, Postgraduate Institute of Medical Education and Research, Chandigarh-160 012, India.
Majumdar
S
S
Vohra
H
H
D000818:Animals; D020013:Calcium Signaling / Q000187:drug effects* / Q000502:physiology; D004748:Entamoeba histolytica / Q000737:chemistry*; D037161:Galectins / Q000737:chemistry / Q000494:pharmacology*; D005786:Gene Expression Regulation / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D006790:Host-Parasite Interactions / Q000235:genetics / Q000502:physiology*; D006801:Humans; D020935:MAP Kinase Signaling System / Q000187:drug effects* / Q000502:physiology; D015800:Protozoan Proteins / Q000494:pharmacology*
D037161:Galectins; D015800:Protozoan Proteins
J Muscle Res Cell Motil. 2001;22(6):521-34
12038586
J Biol Chem. 1989 May 15;264(14 ):8179-84
2498309
Nature. 1970 Aug 15;227(5259):680-5
5432063
Ciba Found Symp. 1992;164:98-108; discussion 108-12
1356716
Ciba Found Symp. 1992;164:36-42; discussion 43-9
1327681
Exp Parasitol. 1996 Mar;82(2):164-70
8617343
Proc Natl Acad Sci U S A. 1984 Apr;81(7):2117-21
6326105
Am J Physiol Renal Physiol. 2002 May;282(5):F910-20
11934702
Immunology. 1992 Jun;76(2):242-50
1634248
Trans R Soc Trop Med Hyg. 1978;72(4):431-2
212851
Proc Natl Acad Sci U S A. 1979 Sep;76(9):4350-4
388439
Annu Rev Microbiol. 1992;46:65-94
1444269
Physiol Rev. 2001 Apr;81(2):807-69
11274345
Parasitol Today. 1996 Apr;12(4):145-50
15275223
J Immunol. 1992 Feb 15;148(4):1188-96
1737935
Trends Microbiol. 1996 May;4(5):191-7
8727599
Infect Immun. 1988 Jun;56(6):1505-12
2897335
Infect Immun. 2001 May;69(5):3382-8
11292761
J Infect Dis. 1989 Mar;159(3):420-9
2536786
Prostaglandins. 1997 Jun;53(6):411-21
9261861
Infect Immun. 1995 Nov;63(11):4253-60
7591055
Methods Enzymol. 1995;253:98-104
7476421
J Infect Dis. 1985 Sep;152(3):542-9
2863317
Infect Immun. 1990 Jan;58(1):43-7
2294057
J Biol Chem. 1951 Nov;193(1):265-75
14907713
Physiol Rev. 2001 Jan;81(1):153-208
11152757
J Clin Invest. 1987 Nov;80(5):1238-44
2890654
Clin Infect Dis. 1995 Jun;20(6):1453-64; quiz 1465-6
7548493
Adv Second Messenger Phosphoprotein Res. 1993;28:81-9
8398421
Biochem Biophys Res Commun. 1991 Oct 15;180(1):209-15
1930217
Cell Motil Cytoskeleton. 1995;32(1):37-45
8674132
Gastroenterology. 1986 Jun;90(6):1972-7
3009262
J Pharmacol Exp Ther. 2002 Jun;301(3):852-66
12023512