Award details

The role of CD45 isoforms in lymphocyte signalling and function

Reference	BB/C507288/1
Principal Investigator / Supervisor	Dr Denis Alexander
Co-Investigators / Co-Supervisors	Dr Nicholas Holmes
Institution	Babraham Institute
Department	Babraham Institute Department
Funding type	Research
Value (£)	202,215
Status	Completed
Type	Research Grant
Start date	07/01/2005
End date	06/01/2007
Duration	24 months

Abstract

The CD45 tyrosine is expressed abundantly on all nucleated haematopoietic cells. It is an essential molecule for normal signalling in both T and B lymphocytes. Alternative splicing generates up to eight CD45 isoforms of which CD45RB, CD45RABC and CD45R0 are dominant in murine lymphocytes. Whereas B cells express mainly CD45RABC (B220), alternative splicing of CD45 is tightly regulated in T cell development and activation. The Big Idea driving this proposal is that different CD45 isoforms play distinct roles in T and B cell functions, thereby regulating immune responses, and that if we understood the molecular mechanisms involved in this process, we would then be in a better position to manipulate CD45 isoforms pharmaceutically in a rational manner. We have generated unique mouse model systems that allow us to address the question of CD45 isoform function in vivo, namely, transgenic mouse lines expressing the CD45RABC, CD45RB or CD45R0 isoforms on a CD45-null background. We plan to use these transgenic lines to carry out a systematic comparison of the molecular actions of the different CD45 isoforms in regulating T and B cell functions and signal transduction pathways in the context of immune responses in the intact animal. T cell development and functions will be investigated using FACS analysis. Comparative analysis of the different CD45 isoform mice will be carried out with respect to: immune responses to T-dependent antigen, T cell activation and proliferation, cytokine responses and TH1/TH2 differentiation, cytotoxicity; modulation of CD28 and CTLA-4 co-regulation, chemotaxis, and lymphocyte survival in vivo and in vitro. These functional assays will be related to the molecular mechanisms of action of CD45 isoforms by assessing: the hetero- and homodimerisation of CD45 isoforms at the cell surface as measured by Fluorescence Resonance Energy Transfer (FRET: collaboration with Debrecen University); the differential regulation of CD45 isoforms of Lck and Fyn tyrosine kinases and of T cell signalling pathways. The striking differences that we have noted between the actions of CD45R0 and CD45RB in B compared to T cells will be assessed by analysing our newly generated CD45RABC transgenic lines. In particular we will analyse: B cell development, proliferation and signal transduction and relate our findings to data obtained by FRET studies investigating the association of CD45 isoforms with the B cell antigen receptor, CD19 and CD22. An important element of our studies will be to relate CD45 expression levels at the cell surface with respect to lymphocyte function so that we can distinguish between the specific actions of CD45 isoforms and differences which may be due to varying levels of CD45 expression at the cell surface. The project will elucidate one of the outstanding mysteries remaining in the CD45 research field.

Summary

unavailable

Committee	Closed Committee - Biochemistry & Cell Biology (BCB)
Research Topics	X – not assigned to a current Research Topic
Research Priority	X – Research Priority information not available
Research Initiative	X - not in an Initiative
Funding Scheme	X – not Funded via a specific Funding Scheme

I accept the terms and conditions of use (opens in new window)

export PDF file

back to list new search