Cargo- and adaptor-specific mechanisms regulate clathrin-mediated endocytosis

Clathrin-coated pit size and dynamic behavior varies with low density lipoprotein receptor (LDLR) expression levels in a manner dependent on the LDLR-specific adaptors, Dab2 and ARH

Plasma Cholesteryl Ester Transfer Protein (CETP) in Relation to Human Pathophysiology

Plasma CETP was initially isolated as a highly purified 74 kD protein. The human CETP gene is located at chromosome 16q13, near the locus of the lecithin cholesterol acyltransferase (LCAT) gene. The CETP gene consists of 16 exons, spanning 25 kb. The CETP mRNA encodes 476 amino acids. The mature CETP contains four N-linked sugars with a variable glycosylation site of 341Asn. CETP mRNA is expressed in various tissues, but liver cells, adipocytes, and macrophages are abundant sources. One of the determinants of high density lipoprotein (HDL) neutral lipid composition is plasma CETP. In incubated human plasma, transfer and equilibration of (LCAT)-generated cholesteryl ester (CE) is found. Humans, hamsters, guinea pigs, and chickens belong to a group with intermediate CETP activity. Plasma CETP binds neutral lipids CE or triglyceride (TG), and phospholipid (PL) on HDL3, but CETP selectively promotes an exchange of CE and TG among lipoproteins. On the one hand, HDL-TG can be hydrolyzed by hepatic lipase, and on the other hand, plasma CETP decreases HDL particle size via CE/TG exchange between chylomicron/VLDL and HDL. Thus, CETP thereby accelerates the catabolic rate of HDL apolipoproteins. CETP enhances HDL remodeling from large HDL to small subclasses including pre-HDL. However, CETP deficiency would decrease cholesterol esterification rate, thereby inhibiting maturation of preb-HDL to α-migrating spherical HDL. Therefore, in CETP deficiency, large-to-small HDL remodeling is decreased and preb-HDL catabolism is also decreased. © 2010 Elsevier Inc. All rights reserved.[Book Chapter

Conserved epigenomic signals in mice and humans reveal immune basis of Alzheimer’s disease

Alzheimer’s disease (AD) is a severe1 age-related neurodegenerative disorder characterized by accumulation of amyloid-β (Aβ) plaques and neurofibrillary tangles, synaptic and neuronal loss, and cognitive decline. Several genes have been implicated in AD, but chromatin state alterations during neurodegeneration remain uncharacterized. Here, we profile transcriptional and chromatin state dynamics across early and late pathology in the hippocampus of an inducible mouse model of AD-like neurodegeneration. We find a coordinated downregulation of synaptic plasticity genes and regulatory regions, and upregulation of immune response genes and regulatory regions, which are targeted by factors that belong to the ETS family of transcriptional regulators, including PU.1. Human regions orthologous to increasing-level enhancers show immune cell-specific enhancer signatures as well as immune cell expression quantitative trait loci (eQTL), while decreasing-level enhancer orthologs show fetal-brain-specific enhancer activity. Notably, AD-associated genetic variants are specifically enriched in increasing-level enhancer orthologs implicating immune processes in AD predisposition. Indeed, increasing enhancers overlap known AD loci lacking protein-altering variants and implicate additional loci that do not reach genome-wide significance. Our results reveal new insights into the mechanisms of neurodegeneration and establish the mouse as a useful model for functional studies of AD regulatory regions

Analysis of lipid transfer activity between model nascent HDL particles and plasma lipoproteins: implications for current concepts of nascent HDL maturation and genesis[S]

The specifics of nascent HDL remodeling within the plasma compartment remain poorly understood. We developed an in vitro assay to monitor the lipid transfer between model nascent HDL (LpA-I) and plasma lipoproteins. Incubation of α-125I-LpA-I with plasma resulted in association of LpA-I with existing plasma HDL, whereas incubation with TD plasma or LDL resulted in conversion of α-125I-LpA-I to preβ-HDL. To further investigate the dynamics of lipid transfer, nascent LpA-I were labeled with cell-derived [3 H]cholesterol (UC) or [3H]phosphatidylcholine (PC) and incubated with plasma at 37°C. The majority of UC and PC were rapidly transferred to apolipoprotein B (apoB). Subsequently, UC was redistributed to HDL for esterification before being returned to apoB. The presence of a phospholipid transfer protein (PLTP) stimulator or purified PLTP promoted PC transfer to apoB. Conversely, PC transfer was abolished in plasma from PLTP−/− mice. Injection of 125I-LpA-I into rabbits resulted in a rapid size redistribution of 125I-LpA-I. The majority of [3H]UC from labeled r(HDL) was esterified in vivo within HDL, whereas a minority was found in LDL. These data suggest that apoB plays a major role in nascent HDL remodeling by accepting their lipids and donating UC to the LCAT reaction. The finding that nascent particles were depleted of their lipids and remodeled in the presence of plasma lipoproteins raises questions about their stability and subsequent interaction with LCAT