Cellular membranes are not simple barriers, and the appropriate membrane composition is essential to ensure proper function of the membrane. In fact, dysfunction as a result of altered membrane composition has been observed in a wide range of diseases including cancers, neurodegenerative and age-related diseases. The composition of the membrane is known to impact its key properties including permeability, curvature, and fluidity;however, the lipid processing pathways and regulators that affect these composition changes have not yet been identified. This is largely due to the fact that in vivo studies of membrane dynamics have been limited, because they require high levels of isotope enrichment to obtain the resolution required to analyze membrane lipids in detail. In the Van Gilst lab, I developed stable isotope enrichment strategies in C. elegans that allow for the quantification of dietary carbon into the fatty acids of the animal. These isotope feeding strategies provide the enrichment levels required for flux analysis of phospholipid membrane dynamics. In this proposal, I will expand the scope of these stable isotope tracer methods to assay the turnover and synthesis of the acyl chains and phospholipid head groups in membranes via gas chromatography/mass spectrometry (GC/MS) and liquid chromatography/mass spectometry (LC/MS), respectively. In doing so, I hope to define many of the pathways that impact membrane composition and its ability to respond to stress and ultimately contribute to the overall understanding of membrane biology and dynamics. One of the most dramatic impacts of membrane composition is in aging, where the phospholipids begin to contain drastically more saturated fatty acids, ultimately making the membranes much more rigid and negatively impacting their function. As examples, the increased saturation index in the aged membrane can affect diffusion properties, transporter function, vesicle fusion, and even signaling. The progressive accumulation of saturated fat in the membranes over aging has been theorized as a major contributor to aging and aging-related dysfunction. The genetic tools of C. elegans will allow us to determine the relative contribution of membrane turnover on the overall membrane composition in young and old animals. The goal of this proposal is to define the genetic regulators and pathways that influence membrane aging and, in doing so, contribute to the understanding of how membrane biology impacts the aging process.
The phospholipid composition of the membrane has a dramatic impact on the membrane's ability to function properly, and altered membrane composition has been associated with a wide array of diseases including cancers, neurodegenerative and age-related diseases. However, the mechanisms that are responsible for the aberrant changes in membrane composition have not yet been identified. Here, I will perform an in vivo study of membrane dynamics and maintenance in C. elegans to define the pathways that regulate membrane composition and how those pathways are altered during aging.
|Amrit, Francis Raj Gandhi; Steenkiste, Elizabeth Marie; Ratnappan, Ramesh et al. (2016) DAF-16 and TCER-1 Facilitate Adaptation to Germline Loss by Restoring Lipid Homeostasis and Repressing Reproductive Physiology in C. elegans. PLoS Genet 12:e1005788|
|Dancy, Blair C R; Chen, Shaw-Wen; Drechsler, Robin et al. (2015) 13C- and 15N-Labeling Strategies Combined with Mass Spectrometry Comprehensively Quantify Phospholipid Dynamics in C. elegans. PLoS One 10:e0141850|
|Ratnappan, Ramesh; Amrit, Francis R G; Chen, Shaw-Wen et al. (2014) Germline signals deploy NHR-49 to modulate fatty-acid ?-oxidation and desaturation in somatic tissues of C. elegans. PLoS Genet 10:e1004829|