Mutational Analysis of CD127 and Its Role in Immunological Diseases
Interleukin (IL) -7 is an essential non-redundant cytokine that influences T-cell differentiation, proliferation, homeostasis and T-cell functions. In T-cells, IL-7 signals are transduced via IL-7's heterodimeric receptor composed of a common, γ chain (CD132) and an IL-7 specific, α chain (CD127). In light of the many roles that IL-7 plays in T-cell biology, it is no surprise that CD127 expression is tightly regulated in T-cells. In this study, I explore the effects that disease specific mutations in CD127 have on CD127 expression, regulation and signal transduction using an in vitro T-cell model. Here I specifically examined four disease associated mutations of CD127: P132S associated with severe combined immunodeficiency; L242_L243insNPC associated with T-cell acute lymphoblastic leukemia; I356V & T244I associated with autoimmune diseases like multiple sclerosis, rheumatoid arthritis and type 1 diabetes. In developing my model, I decided to use Jurkat cells because they expressed high endogenous surface levels of CD132, low endogenous surface levels of CD127 and endogenous STAT5. Jurkat cells were transduced with lentiviruses that induced expression of either WT or one of the four mutant CD127. I found that transduced Jurkat cells produced the WT and all four mutant CD127 proteins. I also found that wild type CD127, I356V, L242_L243insNPC and T244I mutant CD127 proteins were all expressed at the same level on the cell surface. However, I could not detect P132S mutated CD127 protein in its native state on the surface or intracellularly. I also found no differences between the mutant CD127 and wild type CD127 with regards to the level of soluble CD127 transcripts. I found that cell lines expressing L242_L243insNPC, I356V and T244I mutant CD127 protein, down-regulated surface CD127 at high IL-7 doses (25ng/mL) to the same extent as in the cell line expressing wild type CD127 protein. Interestingly, at the low IL-7 dose (1ng/mL) these mutant CD127 cell lines down-regulated surface CD127 to a lesser degree the wild type CD127 cell line. Further studies are required to elucidate whether P132S mutated CD127 is expressed on the surface and if T224I and I356V mutations in CD127 enhance signaling. By understanding CD127 dysregulation and dysfunction in disease states, we can potentially develop therapeutics that can return the function of CD127 to normalcy.
CD127, Autoimmune, SCID, Interleukin-7, Multiple Sclerosis
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Université d'Ottawa / University of Ottawa