Identification of the major functional proteins of prokaryotic lipid droplets

Abstract

Lipid droplets (LDs) are intracellular organelles with neutral lipid cores surrounded by a phospholipid monolayer and coated with various proteins ( 1-3 ). LDs have been found in almost all eukaryotic organisms from yeast to mammals ( 4 ). They interact with other cellular organelles ( 5-8 ), and their dynamics is closely related to the progression of metabolic diseases, such as obesity, fatty liver, type 2 diabetes mellitus, and atherosclerosis ( 9 ). Recent studies have also shown that LDs are involved in the reproduction of infectious hepatitis C virus particles ( 10 ) and in protecting cells from damage ( 11 ). The identifi cation of perilipin, ADRP, and Tip47 (PAT) family proteins has provided useful marker proteins to facilitate the purifi cation of LDs. Recent proteomic studies suggesting that LDs are not simply inert cellular inclusions for the storage of neutral lipids, but rather functional cellular organelles, has established a new era in LD research ( 3,(12)(13)(14)(15)(16)(17)(18).Although LDs are highly dynamic organelles involved in many cellular activities, especially lipid metabolism, the molecular mechanisms that govern LD formation remain largely unknown. The current model of LD biogenesis speculates that LDs are derived from the endoplasmic reticulum (ER) by a process that begins with the accumulation of neutral lipids between the leafl ets of phospholipid bilayers ( 3,19 ). Many studies have attempted to unravel how LDs form and grow, but this hypothesis still lacks direct evidence and the molecular mechanism Abstract Storage of cellular triacylglycerols (TAGs) in lipid droplets (LDs) has been linked to the progression of many metabolic diseases in humans, and to the development of biofuels from plants and microorganisms. However, the biogenesis and dynamics of LDs are poorly understood. Compared with other organisms, bacteria seem to be a better model system for studying LD biology, because they are relatively simple and are highly effi cient in converting biomass to TAG. We obtained highly purifi ed LDs from Rhodococcus sp. RHA1, a bacterium that can produce TAG from many carbon sources, and then comprehensively characterized the LD proteome. Of the 228 LD-associated proteins identifi ed, two major proteins, ro02104 and PspA, constituted about 15% of the total LD protein. (Grant 2009CB919000, Grant 2010CB833703; Grant 2011CBA00900), and the National Natural Science Foundation of China (Grant 30871229, Grant 30971431, and Grant 31000365 Abbreviations: ER, endoplasmic reticulum; LD, lipid droplet; MLDS, microorganism lipid droplet small; MSM, mineral salt medium; NB, nutrient broth; PAT, perilipin, ADRP, and Tip47; PspA, phage shock protein A; TAG, triacylglycerol; TEM, transmission electron microscopy.

Proteomic Study and Marker Protein Identification of Caenorhabditis elegans Lipid Droplets

“…4E). Recovery of fluorescent signals was not observed, indicating that neither DHS-3 was recruited to the bleached LDs from other cellular compartments (arrow-pointed regions) nor translocated to the bleached part from non-bleached part of (19,46) the same LD (arrowhead-pointed region). After 20 min DHS-3::GFP signal was still not detected in the bleached region (supplemental Fig.…”

A Review on The Bioconversion of Lignin to Microbial Lipid with Oleaginous Rhodococcus opacus

“…Transcriptomic and proteomic studies have also identified TAG biosynthetic genes and proteins [48][49][50][51][52][53]. In previous years, the Gram-positive, oleaginous, soil bacterium Rhodococcus opacus has been studied for its ability to accumulate intracellular lipids >20%, based on cell dry weight (CDW) [54][55][56][57][58][59][60].…”

<i>Rhodococcus jostii</i> RHA1 TadA-homolog deletion mutants accumulate less polyhydroxyalkanoates (PHAs) than the parental strain

“…The mechanism by which TadA influences PHA accumulation is not known, but transcriptome data suggests a dynamic balance between pathways that synthesize and consume key metabolic precursors like acetylCoA, acetoacetyl-CoA and 3-hydroxybutyryl-CoA. Previous studies with TAGs further indicate that TadA is similar to apolipoproteins, structural proteins of plasma lipoproteins (Chen et al, 2014;Ding et al, 2012;MacEachran et al, 2010). TadA mutants were first identified in R. opacus PD630 during a genetic screen for transposon mutants that accumulate reduced amounts of TAGs.…”

“…Rhodococcus TadA mutants accumulate up to 30-40% fewer TAGs than the parental wild-type strains displaying defects in lipid body formation (Chen et al, 2014;Ding et al, 2012;MacEachran et al, 2010). Since the accumulation of both PHAs and TAGs manifest as intracellular inclusion bodies, we hypothesized that PHA accumulation in TadA mutants would also be reduced, suggesting that TadA is common to the biogenesis of both PHAs and TAGs.…”