The Role of CD86 Trafficking and Signaling on Myeloma Survival and Proliferation Öffentlichkeit
Moser-Katz, Tyler (Spring 2022)
Published
Abstract
Multiple myeloma is an incurable hematologic malignancy of long-lived antibody secreting plasma cells. Myeloma cells retain numerous features of plasma cell biology including a reliance on signals within the bone marrow microenvironment. In advanced stages, myeloma cells can become extramedullary and survive independently of the bone marrow due to autocrine cytokine signals and cell-cell interactions. One such physical interaction involves the CD28-CD86 module which signals bi-directionally to confer myeloma cell survival and drug resistance. My studies investigate how myeloma cells regulate this interaction and the expression of the CD86 at the plasma membrane. I also demonstrated a role for CD86 in proliferation and further elucidated downstream molecular changes induced by CD28 signaling.
I identified that while several regions of the tail are required for proper trafficking of CD86 out of the Golgi, a specific region for proper transport is a three amino acid-long PDZ binding motif at the C-terminus of the tail. BioID analysis uncovered two PDZ-domain containing proteins, SCRIB and DLG1 as proximal to the CD86 cytoplasmic tail. Deletion of SCRIB and DLG1 in myeloma cell lines results in a decrease in CD86 surface expression, myeloma proliferation and viability. These proteins are important for generating CD86 to the surface where it binds to CD28 and is stabilized. My studies also expand upon the role for CD86 in myeloma, showing a role for CD86 in myeloma proliferation and IMiD resistance. Furthermore, they demonstrate a potential CD28 pro-survival signaling mechanism via SYNTENIN upregulation and may reveal a compensatory role for the ICOS-L-CD28 axis in the absence of CD86.
Table of Contents
Chapter 1: Introduction 1
Abstract 2
Introduction to the Game of Bones 3
Spectrum of Plasma cell dyscrasias 3
The role of the bone marrow microenvironment 9
Myeloma takeover beyond the microenvironment 22
Conclusion 27
Initial Treatment Strategies 29
CD28-CD86 Signaling 33
References 37
Table 1: Defining Stages of Myeloma 49
Figure 1: Bone marrow interactions that promote
myeloma growth and survival. 51
Figure 2: Models for leukocyte and myeloma cell
extravasation. 53
Figure 3: Models for leukocyte and myeloma cell
extravasation. 55
Figure 4: CD28-CD86 binding in different immune
cell types. 56
Chapter 2: PDZ proteins, SCRIB and DLG1, regulate
myeloma surface CD86 expression, growth, and survival 58
Abstract 59
Introduction 60
Materials and Methods 62
Results 68
Discussion 79
Acknowledgments 83
Bibliography 85
Figure 1: CD86 cytoplasmic tail is important for
trafficking to cell surface 95
Figure 2: Multiple Regions of CD86 cytoplasmic
tail are important for trafficking to cell surface 98
Figure 3: CD86 contains a PDZ binding motif
important for surface expression 100
Figure 4: BioID proximity assay identifies numerous CD86
cytoplasmic tail interacting partners 102
Figure 5: SCRIB and DLG1 regulate CD86 surface expression 104
Figure 6: SCRIB and DLG1 are important for cell
growth and viability 106
Figure 7: SCRIB and DLG1 regulate CD86 prosurvival
Signaling 108
Visual Overview: 110
Supplemental Methods 111
Supplementary Table 1 112
Supplementary Figure 1 113
Supplementary Figure 2 115
Supplementary Figure 3 117
Supplementary Figure 4 119
Supplementary Figure 5 120
Supplementary Figure 6 122
Supplementary Figure 7 124
Supplemental Bibliography 125
Chapter 3: Differential expression of CD28
interacting partners CD86 and ICOS-L induces
molecular changes in myeloma cells 126
Introduction 127
Materials and Methods 128
Results 131
Figure 1: Overexpression of CD86FL and TL
results in increased syntenin expression. 132
Figure 2: Silencing of CD86 results in increased
syntenin expression. 134
Figure 3: ICOS-L does not contain a PDZ-binding motif. 135
Figure 4: ICOS-L is upregulated with CD86 and
SYNTENIN silencing. 136
Figure 5: ICOS-L has decreased expression in
CD86-overexpressing cell lines. 137
Discussion 137
Bibliography 141
Chapter 4: The Role of CD28 and CD86 in myeloma cell
Proliferation 143
Introduction 144
Materials and Methods 145
Results 147
Figure 1: Dividing cells express higher CD86. 148
Figure 2: Lenalidomide treatment decreases CD28 and
CD86 expression levels. 149
Discussion 149
Bibliography 151
Chapter 5: Discussion 153
Summary 154
Figure 1: Summary of main research findings. 158
Figure 2: Myeloma CD86 expression and IMiD outcome. 161
Future Directions 165
Concluding Remarks 170
Bibliography 172
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