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The role of scavenger receptor BI in hepatitis - eTheses Repository ...

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58<br />

<strong>The</strong>se data po<strong>in</strong>t to a requirement for the VLDL assembly mach<strong>in</strong>ery for the<br />

packag<strong>in</strong>g <strong>of</strong> viral RNA and structural prote<strong>in</strong>s <strong>in</strong>to <strong>in</strong>fectious HCV LVP, which<br />

are trafficked via the secretory pathway to allow particle release. Intracellular<br />

particles are vulnerable to pre-secretory degradation (109), suggest<strong>in</strong>g that an<br />

<strong>in</strong>fected host cell treats HCV LVPs as VLDLs, target<strong>in</strong>g lipid poor forms for<br />

recycl<strong>in</strong>g <strong>in</strong> the absence <strong>of</strong> sufficient substrate(s).<br />

It is not yet clear how the virus structural prote<strong>in</strong>s and host apoprote<strong>in</strong>s<br />

associate dur<strong>in</strong>g particle assembly. However current data suggests that lipid<br />

droplets (LD), <strong>in</strong>tracellular organelles responsible for lipid storage, are central<br />

to this process. HCV genome replication is believed to occur on membranes<br />

<strong>in</strong> and around the endoplasmic reticulum, mature E1E2 heterodimers also<br />

reside there (181, 220). Core prote<strong>in</strong>, however, translocates to the LDs and is<br />

seen to coat their surface (41, 42, 215), NS5A also localises with the LDs<br />

(280), viral prote<strong>in</strong> association with LDs is essential for the production <strong>of</strong><br />

<strong>in</strong>fectious particles. Core directs the redistribution <strong>of</strong> LDs along the micro-<br />

tubule network br<strong>in</strong>g<strong>in</strong>g them <strong>in</strong>to the vic<strong>in</strong>ity <strong>of</strong> membranes bear<strong>in</strong>g genome<br />

replication complexes (41). It is currently believed that assembly occurs at<br />

these juxtapositions (41, 215), <strong>in</strong>deed numerous studies have demonstrated a<br />

accumulation <strong>of</strong> viral prote<strong>in</strong>s and RNA at these sites (131, 189, 215, 305).<br />

Furthermore, LDs provide a source <strong>of</strong> triglycerides for the load<strong>in</strong>g <strong>of</strong> lipids on<br />

to ApoB (321), suggest<strong>in</strong>g that the VLDL and HCV assembly pathways<br />

converge at this location. (Figure 1-5).

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