Christopher J. R. Loewen

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Recognition of lipids by proteins is important for their targeting and activation in many signaling pathways, but the mechanisms that regulate such interactions are largely unknown. Here, we found that binding of proteins to the ubiquitous signaling lipid phosphatidic acid (PA) depended on intracellular pH and the protonation state of its phosphate(More)
Mitochondrial membrane biogenesis and lipid metabolism require phospholipid transfer from the endoplasmic reticulum (ER) to mitochondria. Transfer is thought to occur at regions of close contact of these organelles and to be nonvesicular, but the mechanism is not known. Here we used a novel genetic screen in S. cerevisiae to identify mutants with defects in(More)
Peripherin/Rds is a tetraspanning membrane protein that has been implicated in photoreceptor outer segment morphogenesis and inherited retinal degenerative diseases. Together with the structurally related protein, Rom-1, it forms a complex along the rims of rod and cone disc membranes. We have compared the oligomeric structure of these proteins from(More)
The endoplasmic reticulum (ER) forms a network of sheets and tubules that extends throughout the cell. Proteins required to maintain this complex structure include the reticulons, reticulon-like proteins, and dynamin-like GTPases called atlastins in mammals and Sey1p in Saccharomyces cerevisiae. Yeast cells missing these proteins have abnormal ER structure,(More)
Synthesis of phospholipids, sterols and sphingolipids is thought to occur at contact sites between the endoplasmic reticulum (ER) and other organelles because many lipid-synthesizing enzymes are enriched in these contacts. In only a few cases have the enzymes been localized to contacts in vivo and in no instances have the contacts been demonstrated to be(More)
Peripherin-2 and Rom-1 are homologous tetraspanning membrane proteins that assemble into noncovalent tetramers and higher order disulfide-linked oligomers implicated in photoreceptor disc morphogenesis. Individuals who coinherit a L185P peripherin-2 mutation and a null or G113E rom-1 mutation are afflicted with retinitis pigmentosa, whereas individuals who(More)
How cells monitor the distribution of organelles is largely unknown. In budding yeast, the largest subdomain of the endoplasmic reticulum (ER) is a network of cortical ER (cER) that adheres to the plasma membrane. Delivery of cER from mother cells to buds, which is termed cER inheritance, occurs as an orderly process early in budding. We find that cER(More)
Synthetic Genetic Array (SGA) analysis is a procedure which has been developed to allow the systematic examination of large numbers of double mutants in the yeast Saccharomyces cerevisiae. The aim of these experiments is to identify genetic interactions between pairs of genes. These experiments generate a number of images of ordered arrays of yeast colonies(More)
The lipid phosphatidic acid is an important metabolic intermediate in the biosynthesis of lipids in all eukaryotic cells, but it is even more than that. Phosphatidic acid is emerging as a lipid that is both composer and conductor, where in addition to its role as biosynthetic precursor (composer) it is also a potent signaling molecule (conductor) that(More)
The organization of the genome is nonrandom and important for correct function. Specifically, the nuclear envelope plays a critical role in gene regulation. It generally constitutes a repressive environment, but several genes, including the GAL locus in budding yeast, are recruited to the nuclear periphery on activation. Here, we combine imaging and(More)