This project will investigate the mechanisms and pathways for the trafficking of surfactant protein-A (SP-A) and surfactant phospholipid (phosphatidylcholine, PC) by the lung and granular pneumocytes (alveolar epithelial type 2 cells). We hypothesize that: (a) SP-A is taken up by receptor-mediated endocytosis through clathrincoated pits. Endocytosis is facilitated by the novel SP-A binding protein P63 (ERGIC 63);(b) upon stimulation with secretagogues or exposure to SP-A, P63 exits the endoplasmic reticulum compartment, possibly in conjunction with the protein 14-3-3, and travels to the plasma membranes;(c) SP-A reaches lamellar bodies both directly from the endoplasmic reticulum and through an endocytic route;(d) surfactant phospholipid (PC) uptake occurs through at least two different pathways, one clathrin-mediated as a complex with SP-A via receptors and the other clathrin-independent, possibly via: (1) specific lipid binding sites on the type 2 cell membrane such as the lamellar body limiting membranes which have been inserted during the process of exocytosis or (2) lipid rafts. We propose that SP-A plays a role in but is not required for maintenance of normal rates of uptake of surfactant PC under basal condition, since a clathrin-independent pathway can be up-regulated in the absence of SP-A. However, lipid uptake cannot be stimulated above basal levels in SP-Adeficient cells. Studies will be carried out with intact rodents, the isolated perfused lung, and primary cultures of type 2 cells.
Specific Aim 1 will examine the interactions of SP-A with the type 2 cell surface membrane protein, P63.
Specific Aim 2 will determine intracellular localization and trafficking of P63.
Specific Aim 3 will use biochemical techniques to establish the pathway for incorporation of SP-A into lamellar bodies via either direct transfer from the endoplasmic reticulum or endocytosis.
Specific Aim 4 will evaluate the clathrindependent and independent pathways for uptake of surfactant PC by type 2 cells using inhibitors specific for each route with SP-A present (wild type) or absent (SP-A KO mouse). These studies will provide evidence defining the pathways regulating the uptake of surfactant components from the alveolar space by the lung and type 2 alveolar pneumocytes.
|Hawkins, Arie; Guttentag, Susan H; Deterding, Robin et al. (2015) A non-BRICHOS SFTPC mutant (SP-CI73T) linked to interstitial lung disease promotes a late block in macroautophagy disrupting cellular proteostasis and mitophagy. Am J Physiol Lung Cell Mol Physiol 308:L33-47|
|Chowdhury, Ibrul; Fisher, Aron B; Christofidou-Solomidou, Melpo et al. (2014) Keratinocyte growth factor and glucocorticoid induction of human peroxiredoxin 6 gene expression occur by independent mechanisms that are synergistic. Antioxid Redox Signal 20:391-402|
|Roszell, Blair R; Tao, Jian-Qin; Yu, Kevin J et al. (2013) Pulmonary abnormalities in animal models due to Niemann-Pick type C1 (NPC1) or C2 (NPC2) disease. PLoS One 8:e67084|
|Roszell, Blair R; Tao, Jian-Qin; Yu, Kevin J et al. (2012) Characterization of the Niemann-Pick C pathway in alveolar type II cells and lamellar bodies of the lung. Am J Physiol Lung Cell Mol Physiol 302:L919-32|
|Rahaman, Hamidur; Zhou, Suiping; Dodia, Chandra et al. (2012) Increased phospholipase A2 activity with phosphorylation of peroxiredoxin 6 requires a conformational change in the protein. Biochemistry 51:5521-30|
|Weibel, Ginny L; Joshi, Michelle R; Jerome, W Gray et al. (2012) Cytoskeleton disruption in J774 macrophages: consequences for lipid droplet formation and cholesterol flux. Biochim Biophys Acta 1821:464-72|
|Maguire, Jean Ann; Mulugeta, Surafel; Beers, Michael F (2012) Multiple ways to die: delineation of the unfolded protein response and apoptosis induced by Surfactant Protein C BRICHOS mutants. Int J Biochem Cell Biol 44:101-12|
|Maguire, Jean Ann; Mulugeta, Surafel; Beers, Michael F (2011) Endoplasmic reticulum stress induced by surfactant protein C BRICHOS mutants promotes proinflammatory signaling by epithelial cells. Am J Respir Cell Mol Biol 44:404-14|
|Beers, Michael F; Hawkins, Arie; Maguire, Jean Ann et al. (2011) A nonaggregating surfactant protein C mutant is misdirected to early endosomes and disrupts phospholipid recycling. Traffic 12:1196-210|
|Zhang, Linghui; Yu, Kevin; Robert, Kyle W et al. (2011) Rab38 targets to lamellar bodies and normalizes their sizes in lung alveolar type II epithelial cells. Am J Physiol Lung Cell Mol Physiol 301:L461-77|
Showing the most recent 10 out of 234 publications