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Speciated human high-density lipoprotein protein proximity profiles.

ABSTRACT: It is expected that the attendant structural heterogeneity of human high-density lipoprotein (HDL) complexes is a determinant of its varied metabolic functions. To determine the structural heterogeneity of HDL, we determined major apolipoprotein stoichiometry profiles in human HDL. First, HDL was separated into two main populations, with and without apolipoprotein (apo) A-II, LpA-I and LpA-I/A-II, respectively. Each main population was further separated into six individual subfractions using size exclusion chromatography (SEC). Protein proximity profiles (PPPs) of major apolipoproteins in each individual subfraction was determined by optimally cross-linking apolipoproteins within individual particles with bis(sulfosuccinimidyl) suberate (BS(3)), a bifunctional cross-linker, followed by molecular mass determination by MALDI-MS. The PPPs of LpA-I subfractions indicated that the number of apoA-I molecules increased from two to three to four with an increase in the LpA-I particle size. On the other hand, the entire population of LpA-I/A-II demonstrated the presence of only two proximal apoA-I molecules per particle, while the number of apoA-II molecules varied from one dimeric apoA-II to two and then to three. For most of the PPPs described above, an additional population that contained a single molecule of apoC-III in addition to apoA-I and/or apoA-II was detected. Upon composition analyses of individual subpopulations, LpA-I/A-II exhibited comparable proportions for total protein (?58%), phospholipids (?21%), total cholesterol (?16%), triglycerides (?5%), and free cholesterol (?4%) across subfractions. LpA-I components, on the other hand, showed significant variability. This novel information about HDL subfractions will form a basis for an improved understanding of particle-specific functions of HDL.

SUBMITTER: Gauthamadasa K

PROVIDER: S-EPMC3006032 | biostudies-literature | 2010 Dec

REPOSITORIES: biostudies-literature

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Speciated human high-density lipoprotein protein proximity profiles.

Gauthamadasa Kekulawalage K Rosales Corina C Pownall Henry J HJ Macha Stephen S Jerome W Gray WG Huang Rong R Silva R A Gangani D RA

Biochemistry 20101123 50

It is expected that the attendant structural heterogeneity of human high-density lipoprotein (HDL) complexes is a determinant of its varied metabolic functions. To determine the structural heterogeneity of HDL, we determined major apolipoprotein stoichiometry profiles in human HDL. First, HDL was separated into two main populations, with and without apolipoprotein (apo) A-II, LpA-I and LpA-I/A-II, respectively. Each main population was further separated into six individual subfractions using siz ...[more]

PMID: 21073165

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Project description:The host range of African trypanosomes is influenced by innate protective molecules in the blood of primates. A subfraction of human high-density lipoprotein (HDL) containing apolipoprotein A-I, apolipoprotein L-I, and haptoglobin-related protein is toxic to Trypanosoma brucei brucei but not the human sleeping sickness parasite Trypanosoma brucei rhodesiense. It is thought that T. b. rhodesiense evolved from a T. b. brucei-like ancestor and expresses a defense protein that ablates the antitrypanosomal activity of human HDL. To directly investigate this possibility, we developed an in vitro selection to generate human HDL-resistant T. b. brucei. Here we show that conversion of T. b. brucei from human HDL sensitive to resistant correlates with changes in the expression of the variant surface glycoprotein (VSG) and abolished uptake of the cytotoxic human HDLs. Complete transcriptome analysis of the HDL-susceptible and -resistant trypanosomes confirmed that VSG switching had occurred but failed to reveal the expression of other genes specifically associated with human HDL resistance, including the serum resistance-associated gene (SRA) of T. b. rhodesiense. In addition, we found that while the original active expression site was still utilized, expression of three expression site-associated genes (ESAG) was altered in the HDL-resistant trypanosomes. These findings demonstrate that resistance to human HDLs can be acquired by T. b. brucei. Keywords: Trypanosoma, VSG, antigenic switching, HDL-resistance Bloodstream stages of the Lister strain 427 T. b. brucei (MiTat 1.2), expressing VSG221, were used in these studies. Cells were cultured in HMI-9 medium with the addition of heat inactivated fetal bovine serum (FBS) (10%) and Serum Plus (10%). T. b. brucei 427-221 is an antigenically stable line and contains a single copy of the vsg221 gene within the 221 expression site (221ES). At a cell density of approximately 1,000,000 cells/ml, T. b. brucei 427-221 were exposed to various amounts of human HDLs for 24 h in a 6 well plate. Surviving trypanosomes were counted using a hemocytometer then diluted into fresh HMI-9 medium and allowed to recover for 5-14 days. Once the cells had grown to a density of approximately 1,000,000 cells/ml, they were once again incubated with human HDLs. Each round of selection was performed with increasing concentrations of human HDLs and freezer stocks were prepared for each surviving population. Over nine months we conducted eight rounds of human HDL selection, resulting in a population of T. b. brucei that survived incubation with 800 μl of human HDLs (160 lytic U).

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Speciated human high-density lipoprotein protein proximity profiles.

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Speciated human high-density lipoprotein protein proximity profiles.

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