NF-kappaB activation pathways induced by T cell costimulation.

Area of Science:

• Immunology
• Molecular Biology
• Cell Signaling

Background:

• Nuclear factor kappa B (NF-kappaB) is a critical transcription factor regulating immune responses.
• Understanding the intricate signaling pathways that activate NF-kappaB is essential for deciphering T cell activation and function.

Purpose of the Study:

• To identify novel components of the costimulation-induced NF-kappaB activation pathway in T cells.
• To elucidate the functional mechanisms of these newly identified signaling proteins.

Main Methods:

• Analysis of knockout mice and T cells deficient in specific signaling proteins.
• Biochemical approaches to investigate protein interactions and enzymatic activities.
• Examination of protein translocation to lipid raft fractions.

Main Results:

• Identified SLP-76, PLC gamma, and Vav1 as crucial components of the NF-kappaB pathway.
• Demonstrated that Vav1 mediates Rac-dependent actin cytoskeleton reorganization.
• Activated PLCgamma1 generates diacylglycerol, a protein kinase C (PKC) activator.
• Established PKCtheta as indispensable for NF-kappaB activation in T cells, requiring recruitment to the immunological synapse.
• Showed that CARD11/CARMA1 and Bcl10 relay signals from the T cell receptor to the IkappaB kinase (IKK) complex.
• Observed constitutive or inducible translocation of NF-kappaB pathway members, including IKKs, to lipid rafts.

Conclusions:

• NF-kappaB activation is orchestrated by an early tyrosine phosphorylation wave leading to multiprotein complex formation.
• PKCtheta and downstream CARD/Bcl10 proteins are vital for transmitting T cell receptor signals to the IKK complex.
• The spatial organization of NF-kappaB activating proteins within lipid rafts is critical for pathway activation.