Thesis Format
Integrated Article
Degree
Master of Science
Program
Microbiology and Immunology
Supervisor
Dikeakos, Jimmy D.
Abstract
Human Immunodeficiency virus type 1 (HIV-1) downregulates major histocompatibility complex I (MHC-I) from the surface of infected cells to evade the immune response by cytotoxic T lymphocytes. To accomplish this, the HIV-1 protein Nef first interacts with Src family kinases (SFKs) to phosphorylate zeta-associated protein 70 producing regulatory post-translational modifications (PTMs). This research investigated the effects of HIV-1 on ZAP-70 regulation, which ZAP-70 PTMs are critical for MHC-I downregulation, and explored the effects of Nef:SFK inhibitors on ZAP-70 PTMs. I found that HIV-1 increases the total level of ZAP-70 along with ZAP-70 pTyr292 and pTyr319 PTMs. Furthermore, these effects are primarily Nef-dependent and are modulated by the related HIV-1 protein Vpu. Pharmacological inhibitors were validated as capable of disrupting the Nef:SFK interaction and variably affected ZAP-70 signalling and MHC-I restoration. Together these findings highlight the multifaceted regulation of ZAP-70 by specific defined HIV-1 proteins.
Summary for Lay Audience
Despite extensive and sustained efforts there still is no functional cure for human immunodeficiency virus type 1 (HIV-1) infection. One obstacle to curing HIV-1 is the ability of the virus to evade human immune system responses. HIV-1 can use its Nef protein to protect infected cells from being killed by a group of immune cells called cytotoxic T lymphocytes (CTLs). To accomplish this, Nef downregulates major histocompatibility complex class I (MHC-I) off the infected cell surface, a molecule which CTLs require to detect virally infected cells. Consequently, detection of HIV-1 infected cells by CTLs is impaired allowing for infected cells to persist.
Nef downregulates MHC-I by using a group of host proteins termed Src family kinases (SFKs) to modify another host protein: zeta-associated protein 70 (ZAP-70). Modification of ZAP-70 by the Nef:SFK interaction initiates a downstream cascade of events which ultimately result in MHC-I downregulation from the infected cell surface. However, the role of HIV-1 proteins in modifying ZAP-70 is still poorly understood. The goal of this research is to characterize the effects of HIV-1 on ZAP-70 modifications, understand which specific HIV-1 proteins mediate this process and to test if ZAP-70 modifications induced by HIV-1 are reversed through pharmacological inhibition.
I observed that HIV-1 increases levels of total ZAP-70 in addition to increasing ZAP-70 modifications involved in MHC-I downregulation. Furthermore, I characterized the essential role of Nef in this process and elucidate a potential new role for the HIV-1 protein Vpu. Additionally, I characterize novel inhibitors against the Nef:SFK interaction and demonstrate their capacity to restore MHC-I on the surface of infected cells. These findings reveal a greater complexity behind HIV-1 regulation of ZAP-70. In doing so, these studies offer new avenues of investigation to determine potential viral targets of pharmacological inhibition. Continually elucidating the mechanisms mediating MHC-I downregulation by HIV-1 is essential to designing anti-viral pharmacological agents with comprehensive functionality.
Recommended Citation
Teplitsky, Jack E., "Regulation of ZAP-70 post-translational modifications by HIV-1 accessory proteins Nef and Vpu" (2024). Electronic Thesis and Dissertation Repository. 10241.
https://ir.lib.uwo.ca/etd/10241