ABCG1 has a critical role in mediating cholesterol efflux to HDL and preventing cellular lipid accumulation.

Here we demonstrate that the ABC transporter ABCG1 plays a critical role in lipid homeostasis by controlling both tissue lipid levels and the efflux of cellular cholesterol to HDL. Targeted disruption of Abcg1 in mice has no effect on plasma lipids but results in massive accumulation of both neutral lipids and phospholipids in hepatocytes and in macrophages within multiple tissues following administration of a high-fat and -cholesterol diet. In contrast, overexpression of human ABCG1 protects murine tissues from dietary fat-induced lipid accumulation.

Expression and regulation of multiple murine ATP-binding cassette transporter G1 mRNAs/isoforms that stimulate cellular cholesterol efflux to high density lipoprotein.

The murine Abcg1 gene is reported to consist of 15 exons that encode a single mRNA (herein referred to as Abcg1-a) and protein. We now demonstrate that (i) the murine gene contains two additional coding exons downstream of exon 1, (ii) transcription involves the use of multiple promoters, and (iii) the RNA undergoes alternative splicing reactions. As a result, three mRNAs are expressed that encode three putative protein isoforms that differ at their amino terminus.

Binding of the AVR4 elicitor of Cladosporium fulvum to chitotriose units is facilitated by positive allosteric protein-protein interactions: the chitin-binding site of AVR4 represents a novel binding site on the folding scaffold shared between the invertebrate and the plant chitin-binding domain.

The attack of fungal cell walls by plant chitinases is an important plant defense response to fungal infection. Anti-fungal activity of plant chitinases is largely restricted to chitinases that contain a noncatalytic, plant-specific chitin-binding domain (ChBD) (also called Hevein domain). Current data confirm that the race-specific elicitor AVR4 of the tomato pathogen Cladosporium fulvum can protect fungi against plant chitinases, which is based on the presence of a novel type of ChBD in AVR4 that was first identified in invertebrates.

LXRs; oxysterol-activated nuclear receptors that regulate genes controlling lipid homeostasis.

The Liver X Receptors (LXR alpha, NR1H3; LXR beta, NR1H2) encode highly homologous transcription factors that are members of the nuclear receptor superfamily of proteins. Both LXR alpha and LXR beta form heterodimers with the obligate partner 9-cis retinoic acid receptor alpha (RXR alpha; NR2B1). LXR/RXR heterodimers function as sensors for cellular oxysterols and, when activated by these agonists, increase the expression of genes that control sterol and fatty acid metabolism/homeostasis.