Download T-CELL RECEPTOR (TCR) PLAY AN IMPORTANT ROLE

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
DINAMIC REGULATION OF miR181a EXPRESSION
IN T-CELLS MATURATION
IMMATURE T-CELLS
DN (CD4-, CD8-)
SP
(CD4-, CD8+)
(CD4+, CD8-)
DP
(CD4+, CD8+)
DN1
DN2
DN3
DN4
(CD44+, CD25-)
(CD44+, CD25+)
(CD44-, CD25+)
(CD44-, CD25-)
ORDER OF
APPEREANCE
DURING
DEVELOPMENT
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 DOESN’T 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USING UNPUBLISHED COMPUTER PROGRAMS, THEY FOUND TARGETS FOR mir181a: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
EFFICACY AND SPECIFICITY OF
shRNA CONSTRUCTS
STRENGHT OF Ca2+ RESPONSE AND
% OF T-CELLS ACTIVATED
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
• NEGATIVE
•Any cell that doesn’t • Any cell that reacts
recognize self MHC is strongly to self
antigen is deleted
deleted
• Ensures functional
matching of receptor,
co-receptor and class
of MHC
•Lineage
commitment