Negative Regulation of Host Innate Antiviral Signaling

123 Pages·2017·2.74 MB·English

by  Qinjie Zhou

University of Miami
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Open Access Dissertations Electronic Theses and Dissertations
2015-03-15
Negative Regulation of Host Innate Antiviral
Signaling
Qinjie Zhou
University of Miami, [email protected]
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https://scholarlyrepository.miami.edu/oa_dissertations/1365
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UNIVERSITY OF MIAMI

NEGATIVE REGULATION OF HOST INNATE ANTIVIRAL SIGNALING

By

Qinjie Zhou

A DISSERTATION

Submitted to the Faculty
of the University of Miami
in partial fulfillment of the requirements for
the degree of Doctor of Philosophy

Coral Gables, Florida

May 2015
©2015
Qinjie Zhou
All Rights Reserved
UNIVERSITY OF MIAMI

A dissertation submitted in partial fulfillment of
the requirements for the degree of
Doctor of Philosophy

NEGATIVE REGULATION OF HOST INNATE ANTIVIRAL SIGNALING

Qinjie Zhou

Approved:

________________ _________________
Edward W. Harhaj, Ph.D. Zhibin Chen, Ph.D.
Associate Professor of Oncology Associate Professor of
Johns Hopkins School of Medicine Microbiology and Immunology

________________ _________________
Wasif N. Khan, Ph.D. Enrique A. Mesri, Ph.D.
Professor of Associate Professor of
Microbiology and Immunology Microbiology and Immunology

________________ ________________
Joyce M. Slingerland, Ph.D. M. Brian Blake, Ph.D.
Professor of Medicine Dean of the Graduate School

________________
Fanxiu Zhu, Ph.D.
Associate Professor of
Biological Science
Florida State University
ZHOU, QINJIE (Ph.D., Microbiology and Immunology)
Negative Regulation of Host (May 2015)
Innate Antiviral Signaling

Abstract of a dissertation at the University of Miami.

Dissertation supervised by Professor Edward W. Harhaj
No. of pages in text (111)

The human T cell leukemia virus type I (HTLV-I) inhibits host antiviral signaling
pathways although the underlying mechanisms are unclear. Here we found that the
HTLV-I Tax oncoprotein induced the expression of SOCS1, an inhibitor of interferon
signaling. Tax required NF-κB, but not CREB, to induce the expression of SOCS1 in T
cells. Furthermore, Tax interacted with SOCS1 in both transfected cells and in HTLV-I
transformed cell lines. Although SOCS1 is normally a short-lived protein, in the presence
of Tax, the stability of SOCS1 was greatly increased. Accordingly, Tax enhanced the
replication of a heterologous virus, vesicular stomatitis virus (VSV), in a SOCS1-
dependent manner. Surprisingly, Tax required SOCS1 to inhibit RIG-I-dependent
antiviral signaling, but not the interferon-induced JAK/STAT pathway. Inhibition of
SOCS1 by RNA-mediated interference in the HTLV-I transformed cell line MT-2
resulted in increased IFN-β expression accompanied by reduced HTLV-I replication and
Gag
p19 levels. Taken together, our results reveal that Tax inhibits RIG-I-dependent
antiviral signaling, in part, by hijacking an interferon regulatory protein.
The transcription factor interferon regulatory factor 7 (IRF7) is a key regulator of
type I interferon and plays essential roles in restricting virus infection and spread. IRF7
activation is tightly regulated to prevent excessive inflammation and autoimmunity;
however, how IRF7 is suppressed by negative regulators remains poorly understood.
Here, we have identified aryl hydrocarbon receptor interacting protein (AIP) as a new
binding partner of IRF7. AIP inducibly interacts with IRF7 upon virus infection and
potently inhibits IRF7-induced type I IFN (IFNα/β) production. Overexpression of AIP
blocks virus-induced activation of IFN, whereas knockdown of AIP by siRNA potentiates
viral-activated IFN production. Consistently, AIP-deficient murine embryonic fibroblasts
are highly resistant to virus infection due to increased production of IFNα/β. AIP inhibits
IRF7 function by antagonizing the nuclear localization of IRF7. Together, our study
identifies AIP as a novel inhibitor of IRF7 and negative regulator of innate RLR
signaling.
DEDICATION

To my parents who support me unconditionally

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ACKNOWLEDGEMENT

I am deeply appreciative and grateful for having the opportunity to pursue my
graduate training at the University of Miami Miller Medical School in the Microbiology and
Immunology program, as well as Johns Hopkins University School of Medicine in the Viral
Oncology program. During the last five-plus years, I was surrounded by outstanding
scientists, staff members, energetic students, and superior post-doctoral fellows.
First and foremost, I want to thank with deepest appreciation my advisor and mentor,
Dr. Edward W. Harhaj, for leading me into the world of academic research with tremendous
patience, encouragement, and mentoring. I’m grateful and feel fortunate to have received his
continuous guidance and the opportunity to work on so many important projects with fruitful
outcomes.
I also express my sincere gratitude to Dr. Alfonso Lavorgna, who is not just my
closest colleague and mentor, but also my best friend and dear brother in the lab. His
patience, generous help, deep understanding, and unconditional support in both of my
professional and personal life have been invaluable.
A special thanks to all my other lab members: Dr. Young Choi, Melissa Bowman;
prior lab members: Dr. Linlin Gao, Dr. Soratree Charoenthongtrakul, Dr. Noula Shembade,
Dr. Kislay Parvatiyar; and Noula’s wife, Raj, for all the immediate help and cover they
provided when I needed it.
Moreover, I thank all my current and prior committee members who always provided
constructive suggestions and guidance along the way: Dr. Zhibin Chen, Dr. Wasif Khan, Dr.
Joyce Slingerland, Dr. Enrique Mesri, and Dr. Shunbin Ning. I also extend a special thanks to
my defense outside-examiner, Dr. Fanxiu Zhu, from Florida State University.
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Last but not least, I thank my dear families, friends in Miami as well as at Hopkins.
Without their support, I would not have made it.
Looking back, it was a journey worth travelling. Thanks to all of you.

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TABLE OF CONTENTS
Page

LIST OF FIGURES ......................................................................................................... viii
Chapter 1 Introduction ........................................................................................................ 1
1.1 Type I IFN signaling pathway and regulation ........................................................... 1
1.1.1 Overview ............................................................................................................ 1
1.1.2 PRRs sensing and recognition ............................................................................ 2
1.1.3 RLR signaling cascade ....................................................................................... 7
1.1.4 Type I IFN production ........................................................................................ 9
1.1.5 IRF3 and IRF7: key IFN regulatory factors ....................................................... 9
1.1.6 Regulation of RLR signaling ............................................................................ 11
1.2 IFNAR signaling pathway and regulation ............................................................... 13
1.2.1 Overview .......................................................................................................... 13
1.2.2 IFNAR binding and recognition ....................................................................... 14
1.2.3 JAK-STAT signaling cascade .......................................................................... 14
1.2.4 Interferon stimulated genes (ISGs) ................................................................... 15
1.2.5 Suppressor of cytokine signaling (SOCS) proteins .......................................... 16
1.3. HTLV-1 and RLR signaling ................................................................................... 17
1.3.1 HTLV-1 infection and associated diseases ....................................................... 17
1.3.2 HTLV-1 transmission and viral replication ...................................................... 17
1.3.3 Viral evasion of antiviral pathways .................................................................. 20
1.3.4 HTLV-1, Tax and antiviral signaling pathways ............................................... 21
1.4 Aryl hydrocarbon receptor (AhR) and AhR interacting protein (AIP) ................... 21
1.4.1 AhR overview ................................................................................................... 21
1.4.2 AhR and virus infection .................................................................................... 22
1.4.3 AIP overview .................................................................................................... 23
1.4.4 AIP and the regulation of the host antiviral response ....................................... 25
Chapter 2 HTLV-1 Tax and innate RLR signaling ........................................................... 26
2.1 Background ............................................................................................................. 26
2.2 Results ..................................................................................................................... 28
2.2.1 Tax induces the expression of SOCS1 ............................................................. 28
2.2.2 Tax requires NF-κB, but not CREB, to up-regulate SOCS1. ........................... 29
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