Biology

Dr. Amit Joshi
University of North Carolina, Chapel Hill, USA

Abstract:

Nascent lipid droplet (LD) and peroxisome formation occurs in the ER membrane. It is not known whether biogenesis of these organelles occurs stochastically in the ER or at ER subdomains with unique protein and lipid composition. Previously, we showed that Pex30 is a reticulon-like protein that tubulates the ER membrane. Unlike the reticulon proteins, Pex30 is not abundant and is localized only at ER subdomains. These ER subdomains are regions where pre-peroxisomal vesicles (PPVs) are generated. Interestingly, Pex30 subdomains are also sites where most nascent LDs form. Mature LDs remain associated with Pex30 subdomains and the same Pex30 subdomain can simultaneously associate with a LD and a PPV. Pex30 subdomains have a unique lipid composition during LD biogenesis. We found that in higher eukaryotes multiple C2 domain containing transmembrane protein (MCTP2) is the functional homologue of Pex30; MCTP2 resides in ER subdomains where most nascent LD biogenesis occurs and that are often associated with peroxisomes. Together, these findings indicate that most LDs and PPVs form and remain associated with conserved ER subdomains and suggest a link between LD and peroxisome biogenesis.