Rhizoctonia bataticola lectin (RBL) induces mitogenesis and cytokine production in human PBMC via p38 MAPK and STAT-5 signaling pathways.
BACKGROUND
Rhizoctonia bataticola lectin (RBL), purified from phytopathogenic fungus Rhizoctonia bataticola is highly mitogenic towards human peripheral blood mononuclear cells (PBMC). The lectin has sugar specificity towards N-glycans and binds to glycoproteins containing complex N-glycans (Nagre et al., Glycoconj J. 2010). In this study, we investigated the role of Mitogen Activated Protein Kinase (MAPK) and Signal Transducers and Activators of Transcription (STAT)-5 signaling in RBL-induced proliferation and production of Th1/Th2 cytokines.


METHODS
Human PBMC were stimulated with RBL and proliferation was determined by tritiated thymidine incorporation assay, cytokine profiles by ELISA and activation of MAPK and STAT-5 by western blotting. RBL binding was monitored by immunofluorescence staining. Expression of IL-2Rα (CD25) was measured by flow cytometry.


RESULTS
The binding and mitogenic activities of RBL were inhibited by glycoproteins- mucin, asialofetuin and fetuin. RBL stimulated expression of IL-2Rα and production of Th1/Th2 cytokines- IL-2, IFN-γ, IL-4 and IL-10. RBL-induced phosphorylation of ERK1/2 and p38 MAPK was detected at 1h and 3h respectively. Significant phosphorylation of STAT-5 (tyr(694)) was observed at 12h. Pharmacological inhibitors of p38 MAPK (SB203580) and JAK/STAT (AG490) but not ERK (PD98059) abrogated proliferation. RBL-induced expression of IL-2Rα and secretion of cytokines were drastically inhibited by SB203580 and AG490.


CONCLUSIONS
RBL-induced proliferation and production of Th1/Th2 cytokines are mediated via p38 MAPK and STAT-5 signaling.


CONCLUSIONS
RBL, a lectin with complex sugar specificity, is strongly mitogenic to human PBMC and stimulates the production of Th1 and Th2 cytokines. The results identified the signaling mechanism underlying the immunostimulatory activity of RBL.
Pujari
Radha
R
National Centre for Cell Science, Ganeshkhind, Pune 411007, India.
Nagre
Nagaraja N
NN
Chachadi
Vishwanath B
VB
Inamdar
Shashikala R
SR
Swamy
Bale M
BM
Shastry
Padma
P
D015153:Blotting, Western; D049109:Cell Proliferation / Q000187:drug effects; D016207:Cytokines / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D005656:Fungal Proteins / Q000378:metabolism / Q000494:pharmacology*; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D007371:Interferon-gamma / Q000378:metabolism; D016753:Interleukin-10 / Q000378:metabolism; D007376:Interleukin-2 / Q000378:metabolism; D053645:Interleukin-2 Receptor alpha Subunit / Q000378:metabolism; D015847:Interleukin-4 / Q000378:metabolism; D037102:Lectins / Q000378:metabolism / Q000494:pharmacology*; D007963:Leukocytes, Mononuclear / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D008934:Mitogens / Q000378:metabolism / Q000494:pharmacology; D011485:Protein Binding; D011725:Pyridines / Q000494:pharmacology; D012232:Rhizoctonia / Q000378:metabolism*; D050799:STAT5 Transcription Factor / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D020032:Tyrphostins / Q000494:pharmacology; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
D016207:Cytokines; D004791:Enzyme Inhibitors; D005656:Fungal Proteins; D007093:Imidazoles; D007376:Interleukin-2; D053645:Interleukin-2 Receptor alpha Subunit; D037102:Lectins; D008934:Mitogens; D011725:Pyridines; D050799:STAT5 Transcription Factor; D020032:Tyrphostins; C095512:alpha-cyano-(3,4-dihydroxy)-N-benzylcinnamide; D016753:Interleukin-10; D015847:Interleukin-4; D007371:Interferon-gamma; D048051:p38 Mitogen-Activated Protein Kinases; C093642:SB 203580