Leukotrienes (LTs) are members of the eicosanoid family of bioactive signaling molecules derived from the substrate arachdonic acid (AA). LTs are lipid signaling molecules that contribute to the initiation and amplification of the innate and adaptive immune responses. LTs are mediators of asthma and allergic rhinitis, as demonstrated by clinical studies, and studies using knockout animals for the biosynthetic enzymes and receptors. Recently, they have been implicated in the chronic vascular inflammation of atherosclerosis. LTs B4, C4, D4 and E4 function to recruit and activate leukocytes in inflamed tissue, and also regulate the function of endothelial cells, and vascular and airway smooth muscle. The formation of LTC4, the parent cysteinyl LT, requires the functional interaction of at least four proteins on the nuclear envelope. These are cytosolic phospholipase A2 (cPLA2), 5-lipoxygenase (5-LO), the 5- lipoxygenase-activating protein (FLAP), and LTC4 synthase;the metabolism of LTA4 by LTA4 hydrolase (LTA4-H) yields LTB4. Recently, we have shown that 5-LO, FLAP, and LTC4 synthase are assembled in novel macromolecular complexes on the nuclear envelope to initiate LT synthesis. These complexes include an additional FLAP-associated protein, Associated Protein-10 kDa (AP-10), and other proteins. AP-10 dissociates from FLAP concurrent with complex formation, suggesting it has an important regulatory role in LT formation. However, neither its identity nor the signals controlling its dissociation from FLAP are known. The intracellular signals that initiate and sustain the association of 5-LO with FLAP and also the overall assembly of the complex are unknown. One possibility is that sustained intracellular calcium levels are required for both membrane targeting of 5-LO and its association with FLAP. Alternatively, the movement of 5-LO to the nuclear envelope and its incorporation into LT membrane synthetic may be under separate controls. The broad, long-term objective of this proposal is to determine how the assembly of LT membrane synthetic complexes is regulated and to identify each of the components and their roles.

Public Health Relevance

LTs are central to the pathogenesis of asthma and renal disease and inflammation. They are also critical for host defense to infection. The studies proposed in this application will identify novel molecular mechanisms for these diseases and, potentially, novel therapeutic targets.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Scientist Development Award - Research & Training (K01)
Project #
5K01DK089145-02
Application #
8325185
Study Section
Diabetes, Endocrinology and Metabolic Diseases B Subcommittee (DDK)
Program Officer
Rankin, Tracy L
Project Start
2011-09-01
Project End
2016-03-31
Budget Start
2012-04-01
Budget End
2013-03-31
Support Year
2
Fiscal Year
2012
Total Cost
$159,521
Indirect Cost
$11,446
Name
Massachusetts General Hospital
Department
Type
DUNS #
073130411
City
Boston
State
MA
Country
United States
Zip Code
02199
Azcutia, Veronica; Routledge, Matthew; Williams, Marcie R et al. (2013) CD47 plays a critical role in T-cell recruitment by regulation of LFA-1 and VLA-4 integrin adhesive functions. Mol Biol Cell 24:3358-68