p56lck signals for regulating thymocyte development can be distinguished by their dependency on Rho function

Area of Science:

• Immunology
• Cell Biology
• Molecular Biology

Background:

• The tyrosine kinase p56lck is vital for pre-T cell differentiation and proliferation.
• The role of other signaling molecules, like GTPase Rho, in p56lck-mediated thymocyte development remains unclear.

Purpose of the Study:

• To investigate the requirement of GTPase Rho in p56lck-mediated signaling pathways during thymocyte development.

Main Methods:

• Generation of double transgenic mice expressing activated p56lck (p56lckF505) and the Rho inhibitor C3 transferase.
• Comparison of thymocyte development in mice with active p56lck on wild-type versus Rho-deficient backgrounds.

Main Results:

• Active p56lck enhances pre-T cell proliferation and increases late pre-T cell numbers, but this effect is abolished in Rho-deficient thymocytes.
• Active p56lck reduces CD2 antigen expression on double-positive (DP) thymocytes, an effect that is Rho-independent.
• Active p56lck inhibits T cell receptor (TCR) expression by interfering with Vbeta-Dbeta rearrangement, a process that is also Rho-independent.

Conclusions:

• p56lck-mediated thymocyte proliferation and CD2 expression are dependent on Rho GTPase function.
• Rho-independent pathways mediate p56lck's effects on TCR expression.
• Signaling pathways regulated by p56lck can be distinguished by their dependency on Rho function.