Subcellular localization of the mosquito sterol carrier protein-2 and sterol carrier protein-x

Abstract

Subcellular distribution of Aedes aegypti sterol carrier protein-2 (AeSCP-2) and AeSCP-x was studied using electron microscopy. In both cultured A. aegypti cells and in the larval midgut, AeSCP-2 was detected mostly in the cytosol, with some labeling mitochondria and nucleus, but not in membranous vesicles. The widespread distribution of AeSCP-2 in the midgut epithelium is consistent with its potential lipid transfer function in all phases of cholesterol absorption. In contrast, AeSCP-x was found mostly in the peroxisome. Differences in the subcellular distribution of AeSCP-2 and AeSCP-x suggest that these two members of the SCP-2 gene family are functionally distinct. Overexpression of AeSCP-2 in A. aegypti cells showed increased localization of AeSCP-2 to cytosol, mitochondria, and nucleus. This is the first report on the nuclear distribution of an SCP. Overexpression of AeSCP-2 resulted in increased cholesterol incorporation in cells, suggesting that AeSCP-2 enhances cholesterol uptake. -Lan, Q., and R. J. Massey. Subcellular localization of the mosquito sterol carrier protein-2 and sterol carrier protein-x.

Identification of mosquito sterol carrier protein-2 inhibitors

“…However, AeSCP-2 differs from the vertebrate SCP-2 in several aspects. In both cultured Aedes aegypti cells and in the larval midgut, AeSCP-2 localizes mostly in the cytosol, which is consistent with the fact that AeSCP-2 lacks the C-terminal peroxisome targeting sequence (6). The coordination site for a ligand in AeSCP-2 is different from the vertebrate SCP-2, in which the hydrophobic moieties of these ligands are oriented at opposite ends of the protein (8).…”

“…Aag-2 cells were seeded at 2 ml of 5 ϫ 10 5 cells/ml in 35 ϫ 10 mm culture dishes. Transfection of AeSCP-2 expression vector was conducted as described (6). AeSCP-2-overexpressing cells were dislodged, diluted 2-fold (5 ϫ 10 4 cells/ml), and dispensed at 0.5 ml/well into 24-well culture dishes.…”

“…The vertebrate SCP-2, SCP-x, and HSD17B4 have a peroxisome localization sequence in the C terminus, targeting these proteins to the peroxisome (1,2,4). The mosquito SCP-2 (AeSCP-2) appears to represent a unique nonperoxisomal and lowmolecular-weight protein in the SCP-2 gene family (5,6).…”

Investigation of the ligand spectrum of human sterol carrier protein 2 using a direct mass spectrometry assay

“…Originally, SCP2 had only been unambiguously identified in higher vertebrates but recently SCP2 sequences have also been found across taxa, including bacteria, archaea, fungi, insects, nematodes and plants [2][3][4][5]. In addition to displaying varied tissue distribution and diverse subcellular locations as well as a broad ligand spectrum, SCP2 domains are found in variable molecular contexts [1].…”

Immuno-histochemical localization of cholesterol binding proteins in Schistocerca gregaria (Forskal)

“…These are synthesized in the fat body and secreted into the hemolymph from where these are transferred to maturing follicles (Osir et al, 1986). These sterol carrier proteins have been identified and immunocytochemically localized in, liver cells (Pandak et al, 2006), rat brain (Horton and Shimomura 1999;Kim and Ong, 2009) and in mosquitoes (Komnick and Giesa, 1994;Lan and Massey, 2004;Schroeder et al, 2000). In addition, intracellular localization of insect sterol carrier protein-2 was successfully done (Seedorf et al, 2000).…”