Expression of CD317 on Hematopoietic Cells: A Dual-Mechanism Regulation.
Shunyou Gong, Youhai H Chen. University Hospitals of Cleveland and Case Western Reserve University School of Medicine, OH; University of Pennsylvania, Philadelphia
Background: CD317 is a glucosyl-phosphatidylinositol (GPI)-anchored protein with unique topology. CD317 was firstly identified as a multiple myeloma antigen and has been demonstrated to be an effective target for the immunotherapy against multiple myeloma. Recently, CD317 has been demonstrated to be expressed, although at much lower intensity, on wide variety of human hematopoietic cells. It was reported that the surface level of CD317 is subject to tight regulation, although the mechanisms regulating its expression on hematopoietic cells have been poorly understood. Obviously, to better employ anti-CD317 immunotherapy for treating multiple myeloma, it has become fundamentally important to clarify the mechanisms regulating the expression of CD317 on hematopoietic cells.
Design: Two strategies were used to explore the possible mechanisms regulating CD317 expression among hematopoietic cells. Firstly, Anti-CD3 antibody was injected intravenously to C57BL/6 naïve mice, and the CD317 expression levels on peripheral T cells were detected by flow cytometry in a time-dependent manner. Secondly, retrovirus-mediated expression vectors carrying tyrosine motif-mutated CD317 were introduced to bone marrow stem cells, and the surface levels of CD317 were decided by flow cytometry. The regulations of CD317 on hematopoietic cells were analyzed thereafter.
Results: In vivo anti-CD3 stimulation dramatically stimulates the up-regulation of CD317 on peripheral T cells, indicating the expression of CD317 is controlled by T cell receptor (TCR) activation. In the meanwhile, Mutations of the two conserved tyrosine residues (Tyr-6 and /or Tyr-8) located on the N-terminus cytoplasmic tail of CD317 significantly increase the surface level of CD317, suggesting the importance of protein motif on the regulation of CD317 expression on hematopoietic cells.
Conclusions: In this study, we demonstrated that the expression of CD317 on hematopoietic cells is controlled by a unique dual-mechanism, namely activation based regulation and motif-based regulation. Our findings are significant for optimizing the anti-CD317 immunotherapy and further elucidating the mechanisms regulating CD317 expression among hematopoietic cells.
Tuesday, March 1, 2011 1:00 PM
Poster Session IV # 156, Tuesday Afternoon