Abdul A. Waheed
How did you get interested in science?
My journey into science was shaped by a combination of inspiring factors and academic interests. One of the key influences was an enthusiastic science teacher in high school who provoked my curiosity with engaging lessons and hands-on experiments. I developed a keen interest in chemistry, particularly organic chemistry, which acted as a driving force to understand the complex molecular structures that govern life’s processes. This interest in molecules and their interactions laid a strong foundation for my later exploration of biological systems at the molecular level.
Biomembranes have emerged as an appealing focal point within biological science, these barriers that define the boundaries of a cell and its organelles play a key role in cellular processes. The curiosity of how molecules cross these lipid bilayers fascinated me and prompted me to develop a deeper interest in understanding their biophysical and functional properties. My Ph.D. thesis was focused on understanding the mysteries of membrane dynamics and their implications in cellular function. During postdoctoral studies, my attention focused on lipid rafts – microdomains within biomembranes that have significant implications in cell signaling. Exploring their role in various processes, including virus assembly, opened up a new avenue that bridged membrane biology and virology.
In essence, my journey into biological science was a symphony of inspiration from mentors, a passion for molecular interactions, and a continuous commitment to understand the fascinating complexities underlying living organisms.
Tell us about the lab where you did this work.
I conducted this research at the laboratory of Dr. Eric Freed at the National Cancer Institute (NCI) in Frederick, Maryland. Dr. Freed is a well-known researcher in the field of molecular virology, with an emphasis on the late stages of the HIV-1 replication cycle. His research focuses on HIV-1 Gag trafficking, virus assembly and release, maturation, and drug resistance. The NCI-Frederick campus is renowned for its state-of-the-art research facilities and its contributions to advancing our understanding of cancer, infectious diseases, and related fields.
Around two decades ago, I started an exciting chapter of my scientific journey by joining Dr. Freed’s lab. My expertise in the field of lipid rafts during my prior postdoctoral work facilitated this transition. This move to Dr. Freed’s lab marked a significant advancement in my career, aligning perfectly with my passionate interest in lipid rafts and their functional significance. Dr. Freed’s lab, renowned for its pioneering research in the late stages of the replication cycle, provided an ideal platform to explore the connections between lipid rafts and HIV-1 assembly. I was able to merge my expertise in lipid rafts with the lab’s primary focus on retroviral assembly. Over time, my research shifted towards investigating host-restriction factors in the HIV-1 life cycle, such as tetherin, TIM-1, SERINC, PSGL-1, and MARCH proteins.
The invaluable guidance and support of Dr. Freed encouraged a sense of confidence that empowered me to undertake ambitious projects. With his support, I embarked on scientific endeavors that stretched my limits, expanded my horizons, and significantly contributed to my scientific and personal growth. The bonds formed with my colleagues in Dr. Freed’s lab transformed it into a second family for me. This bond we shared was instrumental in making the lab a place for vibrant scientific exploration and personal development.
What were the biggest challenges with this study?
One of the major challenges in this study is understanding how disruption of nSMase2, either through siRNA-mediated knockdown or treating virus-producing cells with selective inhibitors like PDDC or DPTIP impairs HIV-1 Gag and GagPol processing, resulting in a profound impairment in particle maturation and infectivity. We hypothesize that alterations in the lipid composition, particularly reduced ceramide levels due to nSMase2 inhibition, impact viral membrane properties. These changes in the biophysical properties of the viral membrane, in turn, hinder GagPol dimerization, a critical step for cleaving the GagPol and Gag precursor proteins into their individual domains, allowing the virus to mature. To investigate these biophysical changes, we use fluorescence probes such as Laurdan to assess viral membrane fluidity. We employ FRET between fluorescently tagged GagPol proteins to investigate GagPol dimerization under nSMase2 disruption.
To further understand the mechanism of action of nSMase2 inhibitor, we selected PDDC-resistant HIV-1, and mutations that confer resistance to PDDC were mapped to the MA and CA domains of Gag. However, these mutants exhibited only low-level resistance to PDDC. Our objective is to develop high-level resistance to PDDC and identify mutations that confer resistance. These studies will shed some light on the mechanism of action of this nSMase2 inhibitor.
We discovered that nSMase2 disruption significantly impairs the maturation and infectivity of other primate lentiviruses, such as HIV-2 and simian immunodeficiency virus. However, it has a moderate or no effect on non-primate lentiviruses like equine infectious anemia virus and feline immunodeficiency virus, and has no effect on the gammaretrovirus murine leukemia virus (MLV) and alpharetrovirus Rous sarcoma virus. To explore PDDC sensitivity, we examined Gag chimeras from sensitive (HIV-1) and insensitive (MLV) viruses to map determinants of nSMase2 disruption sensitivity. Intriguingly, our findings suggest that HIV-1 Pol is the target of nSMase2 disruption. Currently, we are examining determinants within HIV-1 Pol for sensitivity to nSMase2 disruption.
What are you working on now?
Continuing my research, my focus is on resolving the mechanism behind Gag and GagPol processing defects during nSMase2 disruption. This involves investigating viral membrane biophysical properties, selecting high-level PDDC resistance and identifying mutations, and pinpointing molecular determinants in HIV-1 GagPol that are sensitive to nSMase2 disruption.