MICHAEL SAKALIAN
$420,984
UNIVERSITY OF CALIFORNIA LOS ANGELES
California
National Institute of General Medical Sciences (NIGMS)
Viruses and their hosts are engaged in a constant, dynamic struggle as part of an ongoing evolutionary arms race. It is well established that viruses continually evolve new offensive strategies, like the production of proteins that disrupt host defenses, while hosts develop countermeasures to detect and neutralize viruses. However, a key question that remains is: how do viruses perceive and respond to host cues in real-time? This ability to sense and adapt to the intracellular environment, akin to real-time "decision-making," which helps them decide when to replicate, assemble, or escape, plays a crucial role in their fitness and ability to spread. To understand how viruses sense and respond to their environment, we will study host-derived post-translational modifications (PTMs) of viral proteins. The overarching hypothesis of this proposal is that viral proteins have evolved as substrates for host enzyme-derived PTMs to equip them with molecular sensors to coordinate viral life cycle transitions. Furthermore, we will study how PTMs enable multifunctionality in viral proteins by creating distinct proteoforms. By understanding the molecular mechanisms of viral biosensors, we expect to pinpoint critical viral dependencies, revealing promising targets for antiviral intervention. PTMs, imposed by the host cell, can dramatically alter the functions of viral proteins, influencing their behavior and ultimately the fate of the virus. Our preliminary mass spectrometry phosphoproteomics analysis of alphavirus infection revealed phosphorylation sites at the capsid-glycoprotein interface, likely regulated by plasma membrane-localized kinases, suggesting a functional switch in glycoproteins at the membrane. We similarly identified phosphorylation sites on herpesvirus latency proteins, which we believe may play a role in allowing the viral genome to replicate alongside the host genome during latency. Lastly, we discovered phosphorylation of a SARS-CoV-2 accessory protein by innate immune kinases, suggesting a feedback mechanism that may modify viral protein function in response to immune activation. Our data have led us to three specific areas of inquiry, each forming a distinct research project being conducted by PhD students, a project scientist, and undergraduate trainees: (1) How do viruses navigate through distinct host subcellular locations during their life cycle? (2) How do viruses coordinate their life cycle with the host cell cycle? (3) How do viruses sense, respond to, and exploit the host innate immune system? The projects and questions outlined in this proposal will serve as the foundation for the primary research in my laboratory over the next five years. Our questions seek to establish a new research area centered on the biochemical mechanisms through which viruses act as biosensors of the host signaling environment, how these biosensors adjust their functionality in response to PTMs, and how targeting these sensors may result in innovative antiviral therapies.