A three-decade odyssey in HIV assembly, from transfer RNA to calcium sparks in virological synapse – a potential general principle in protein trafficking.

Title:  A three-decade odyssey in HIV assembly, from transfer RNA to calcium sparks in virological synapse – a potential general principle in protein trafficking. 

Presenter:  Prof Johnson Mak, Griffith University

Abstract: Polarized or precision targeting of protein complexes to their destinations is fundamental to cellular homeostasis, but the mechanism underpinning directional protein delivery is poorly understood. Here, we use the uropod targeting HIV synapse as a model system to show that the viral assembly machinery Gag is co-polarized with the intracellular calcium (Ca2+) gradient and binds specifically with Ca2+. Conserved glutamic/aspartic acids are major Ca2+ binding sites. Deletion or mutation of these Ca2+ binding residues resulted in altered protein trafficking phenotypes, specifically, changes in the Ca2+ -viral protein interaction impacts on homo/hetero-oligomerization of viral proteins that are associated with a protein ubiquitination, resulting in a decline in virion release via uropod protein complex delivery. Our data that show Ca2+–protein binding, via the intracellular Ca2+ gradient, represents a mechanism that regulates intracellular protein trafficking. 

Bio:  Professor Mak is a native of Hong Kong (as well as a Canadian and an Australian) who undertook his undergraduate and post-graduate training at McGill University in Montreal, Canada. During his PhD Johnson worked with Professor Lawrence Kleiman at the McGill AIDS Centre studying packaging of primer tRNA into HIV. He subsequently moved to Melbourne, Australia to continue work on HIV assembly at the Burnet Institute. Johnson also held appointments with Monash University, Deakin University and CSIRO AAHL. Johnson is currently a Professor at the Institute for Glycomics, Griffith University, Gold Coast.

Johnson has a broad research portfolio in HIV having studied primer tRNAs in retroviruses, genomic RNA packaging and dimerization, cholesterol and lipids in HIV, viral-host interactions, imaging of HIV and analysis of recombination and mutation in HIV using next generation sequencing. His team pioneered the production of full-length recombinant HIV Gag for biochemical and biophysical analyses of HIV assembly. Recently Johnson and his team have described a pre-entry priming process for HIV, as well as revealed novel biology between HIV and glycans. Other works include the role of calcium in protein trafficking during HIV synapse formation.