posted on 2022-02-01, 19:09authored byChandan Kishor, Belinda L. Spillings, Johana Luhur, Corinne A. Lutomski, Chi-Hung Lin, William J. McKinstry, Christopher J. Day, Michael P. Jennings, Martin F. Jarrold, Johnson Mak
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 copolarized with the intracellular
calcium (Ca2+) gradient and binds specifically with Ca2+. Conserved glutamic/aspartic acids flanking endosomal sorting
complexes required for transport binding motifs are major Ca2+ binding sites. Deletion or mutation of these Ca2+ binding
residues resulted in altered protein trafficking phenotypes, including
(i) changes in the Ca2+–Gag distribution relationship
during uropod targeting and/or (ii) defects in homo/hetero-oligomerization
with Gag. Mutation of Ca2+ binding amino acids is associated
with enhanced ubiquitination and 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.