Chlamydia trachomatis infection leads to defined alterations to the lipid droplet proteome in epithelial cells

HECTOR A. SAKA; J WILL THOMPSON; CHEN, YS; LAURA G. DUBOIS; JOEL T. HAAS; M. ARTHUR MOSELEY; RAPHAEL H. VALDIVIA

New Orleans

Encuentro; CBRS 2015 Biennial Meeting; 2015

Chlamydia Basic Research Society

Background and Significance: Chlamydia trachomatis (CT) is a main cause of genital and ocular diseases worldwide. Acquisition of lipids from the host cell is a critical step in chlamydial replication, which occurs inside a membrane-bound vacuole or "inclusion". Lipid droplets (LD) are ubiquitous, ER-derived lipid-rich organelles. LDs accumulate at the periphery of, and translocate into the chlamydial inclusion. Objectives: To study Chlamydia-LD interactions at the molecular level and to evaluate the impact of LD biogenesis in chlamydial growth. Methods: We used label-free quantitative mass spectrometry to carry-out a comparative analysis of the LD proteome from infected and CT-infected HeLa cells. We performed IFU assays in mouse embryonic fibroblasts derived from wild type or diacylglycerol-acyltransferases 1 and 2 double knock-out animals (dgat1/2-/-) to evaluate the impact of LD biogenesis on chlamydial growth. Results: LDs isolated from CT-infected cells were enriched in proteins related to lipid metabolism, biosynthesis and LD-specific functions. Consistent with the observation that LDs intimately associate with the inclusion, a subset of inclusion membrane proteins (Incs) co-purified with LD protein extracts. Finally, genetic ablation of LDs negatively affected the generation of C. trachomatis infectious progeny. Conclusions: Distinct changes to the LD proteome occur in response to CT-infection. Lack of LD formation in dgat1/2-/- cells correlated with impaired generation of infectious progeny, indicating that LDs contribute to optimal C. trachomatis growth.