StaR-related lipid transfer-like domain-containing protein CLDP43 affects cardiolipin synthesis and mitochondrial function in Trypanosoma brucei.

Cardiolipin is known to interact with bacterial and mitochondrial proteins and protein complexes. Unlike in Escherichia coli and Saccharomyces cerevisiae, the synthesis of cardiolipin is essential for growth of Trypanosoma brucei parasites in culture. Inhibition of cardiolipin production has been shown to result in major changes in the T. brucei proteome and energy metabolism, with CLDP43, a mitochondrial protein containing a StaR-related lipid transfer (START)-like domain, being depleted in a cardiolipin-dependent way. We now show that in T. brucei procyclic forms lacking CLDP43, cardiolipin metabolism and mitochondrial function are affected. Using quantitative and qualitative lipid analyses, we found that while steady-state levels of cardiolipin were elevated in CLDP43 knock-out parasites compared to parental cells, de novo formation of cardiolipin was down-regulated. In addition, depletion of CLDP43 resulted in partial loss of mitochondrial membrane potential and decreased ATP production via substrate level phosphorylation. Recombinant CLDP43 was found to bind cardiolipin and phosphatidic acid in lipid overlay experiments, suggesting that it may be involved in transport or synthesis of cardiolipin or its precursors in T. brucei

Statistical Analysis of the Processes Controlling Choline and Ethanolamine Glycerophospholipid Molecular Species Composition

The regulation and maintenance of the cellular lipidome through biosynthetic, remodeling, and catabolic mechanisms are critical for biological homeostasis during development, health and disease. These complex mechanisms control the architectures of lipid molecular species, which have diverse yet highly regulated fatty acid chains at both the sn1 and sn2 positions. Phosphatidylcholine (PC) and phosphatidylethanolamine (PE) serve as the predominant biophysical scaffolds in membranes, acting as reservoirs for potent lipid signals and regulating numerous enzymatic processes. Here we report the first rigorous computational dissection of the mechanisms influencing PC and PE molecular architectures from high-throughput shotgun lipidomic data. Using novel statistical approaches, we have analyzed multidimensional mass spectrometry-based shotgun lipidomic data from developmental mouse heart and mature mouse heart, lung, brain, and liver tissues. We show that in PC and PE, sn1 and sn2 positions are largely independent, though for low abundance species regulatory processes may interact with both the sn1 and sn2 chain simultaneously, leading to cooperative effects. Chains with similar biochemical properties appear to be remodeled similarly. We also see that sn2 positions are more regulated than sn1, and that PC exhibits stronger cooperative effects than PE. A key aspect of our work is a novel statistically rigorous approach to determine cooperativity based on a modified Fisher's exact test using Markov Chain Monte Carlo sampling. This computational approach provides a novel tool for developing mechanistic insight into lipidomic regulation

Cardiolipin as key lipid of mitochondria in health and disease. 2nd Edition, Florence, Italy, September 30-October 1, 2015

The second edition of the workshop dedicated to cardiolipin, the signature lipid of mitochondria, was held as a satellite meeting of the 13th Euro Fed Lipid international congress in Florence, Italy, at the end of September 2015. During the workshop various aspects of basic cardiolipin functions in biomembranes of prokaryotes and animal cells were discussed, highlighting connections between cardiolipin research and human physiology in particular. Alteration of the cardiolipin species pattern and a parallel increase of monolysocardiolipin is the hallmark of Barth syndrome, an X linked genetic disease. Furthermore literature reports suggest the involvement of cardiolipin in other pathologies associated with an imbalance in bioenergetic functions, such as diabetes. The Cardiolipin Workshop was a low budget meeting sponsored by the University of Bari Aldo Moro and the Barth Syndrome Foundation. The organizers are grateful to the invited speakers, poster presenters and chairpersons as they supported the meeting by sustaining their travel and lodging expenses. Before the starting of the scientific sessions, the families of Italian boys affected by Barth syndrome (recently affiliated with the Barth Syndrome Foundation, USA) could meet scientists, biologists and pediatricians involved in research, diagnosis and cure of the disease. The family meeting was chaired by Daniela Toniolo, who discovered the tafazzin gene in 1997