JOURNAL CLUB, 28th september 2007 T-CELL ACTIVATION T-CELLS ARE ABLE TO DISTINGUISH BETWEEN SELF AND NON SELF ANTIGENS (Ag) T-CELL RECEPTOR (TCR) PLAY AN IMPORTANT ROLE, BECAUSE IT RECOGNIZES Ag PRESENTED BY APC IN MHC AND THIS LEADS TO THE INDUCTION OF INTRACELLULAR SIGNALING AND T-CELL RESPONSES T-CELLS RESPONSIVENESS AND TCR SIGNALING VARY WITH T-CELL DEVELOPMENT miRNA WERE RECENTLY DISCOVERED TO BE DIFFERENTIALLY EXPRESSD DURING HEMATOPOIETIC DIFFRENTIATION AND THEY MAY BE INVOLVED IN CONTROLLING THE DEVELOPMENT OF IMMUNE SYSTEM RESULTS DN (CD4 -, CD8 - ) SP (CD4 -, CD8 + ) (CD4 +, CD8 - ) DP (CD4 +, CD8 + ) IMMATURE T-CELLS DN1 (CD44 +, CD25 - ) DN2 (CD44 +, CD25 + ) DN3 (CD44 -, CD25 + ) DN4 (CD44 -, CD25 - ) ORDER OF APPEREANCE DURING DEVELOPMENT DINAMIC REGULATION OF miR181a EXPRESSION IN T-CELLS MATURATION miR181a EXPRESSION AUGMENTS TCR SIGNALING TO ACCESS HOW miR181a AFFECTS TCR SIGNALING: INCREASED EXPRESSION OF miR181a IN 5C.C7 Ag PRIMED CD4 + T-CELLS STIMULATED WITH MCC (AGONIST); TCR SIGNALING STRENGHT ASSESSED BY MESASURING Ca2 + INCREASE HIGH LEVEL OF miR181a AUGMENTS TCR-MEDIATED T-CELLS ACTIVATION miR181a EXPRESSION AUGMENTS TCR SIGNALING TCR SIGNAL INPUT=NUMB OF ANTIGENIC pMHC COMPL. AT T:APC INTERFACE TCR SIGNAL OUTPUT=CALCIUM CONCENTR CHANGES IN CYTOSOL miR181a EXPRESSION INCREASES T CELLS SENSITIVITY miR181a CONVERTS ANTAGONIST INTO AGONIST MCC99R INDUCE CALCIUM INCREASE IN miR181a CELLS MCC99R ALONE STIMULATE EFFECTOR T-CELLS FUNCTION miR181a EXPRESSION DOESNT ALTER CD4 AND TCR DENSITY ON T-CELLS SURFACE WHEN CD28 IS BLOCKED AND miR181a T-CELLS ARE TRETAED WITH MC99R, THEY CAN STILL RESPOND TO THE ANTAGONIST. miR181a MODULATE TCR SENSITIVITY BY CONTROLLING INTRACELLULAR SIGNALING MOLECULES, SUCH AS SHP1 (Lck NEGATIVE REGULATOR) AND ERK1/2 PATHWAYS USING UNPUBLISHED COMPUTER PROGRAMS, THEY FOUND TARGETS FOR mir181a: Lck-SPECIFIC-TYROSIN POHOSPHATASE, SHP-2 AND PTPN22 ERK-SPECIFIC-PHOSPHATASE, DUSP5 AND DUSP6 miR181a REPRESSES MULTIPLE PHOSPHATASE IN T-CELLS miRNA181a INCREASES THE BASAL PHOSPHORILATION LEVELS OF Lck AND ERK miR181a EXPRESSION INHIBITS Lck/SHP1 INTERACTION MECHANISM OF TCR SIGNALING MULTITARGET REPRESSION IS REQUIRED FOR miR181a FUNCTION IN TCR SIGNALING STRENGHT OF Ca 2+ RESPONSE AND % OF T-CELLS ACTIVATED EFFICACY AND SPECIFICITY OF shRNA CONSTRUCTS CONTRIBUTION OF EACH PHOSPHATASE TO Ag DISCRIMINATION miR181a MODULATES NEGATIVE AND POSITIVE SELECTION OF T-CELLS TREATMENT WITH ANTAGOMIR RESTORED PHOSPHATASE/KINASE INVOLVED IN TCR SIGNALING IN DP CELLS INHIBITION OF ERK ACTIVITY CONCLUSIONS miRNAs ARE A NEW CLASS OF REGULATORY MOLECULES IN THE IMMUNE SYSTEM miR181a IS AN INTRINSIC MODULATOR OF TCR SENSITIVITY IN T-CELL DEVELOPMENT (ALTHOUGH OTHER COMPONENTS MAY CONTRIBUTE TO THESE CHANGES IN SENSITIVITY) miRNAs CAN MODULATE MULTIPLE TARGETS AS THEY EXERT A QUANTITATIVE REGULATION THAT ALLOWS A DISCRIMINATIVE SWITHC IN Ag RECOGNITION Paper discussion What is the key experiment? (the one confirming the statement in the title) What is the strongest point? What is the weakest point? and What to do to strenghten it? What is the take home message? (summarize it in a sentence) POSITIVE Any cell that doesnt recognize self MHC is deleted Ensures functional matching of receptor, co-receptor and class of MHC Lineage commitment NEGATIVE Any cell that reacts strongly to self antigen is deleted