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

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28 in HepG2 cells (101). These data indicate that using recombinant soluble proteins to measure E2-receptor interactions can be a poor model of infection. They also established that soluble CD81 LEL neutralisation of HCVpp occurs after virion binding to target cells (101), suggesting that CD81 is not the primary HCV attachment receptor, a view supported by other findings (31, 91, 346). The use of anti-E2 mAbs and comparison of diverse envelope proteins allowed the identification of putative CD81 recognition domains within the major HCV glycoprotein. Mutagenic studies within these regions has both confirmed and eliminated candidate residues. The currently accepted CD81 binding regions are 436-443, 527-535 and 612-619, residue 420 is also involved (81, 99, 237, 265). However, without a crystal structure of HCV E2 it remains unclear how these distant regions engage CD81 and whether other receptors are required to promote CD81 interaction. Antibodies that recognise sites within CD81 binding regions are neutralising and work to develop a vaccine that targets these epitopes is ongoing (145, 147, 236, 237, 307). Scavenger receptor B-I (SR-BI) SR-BI is a multi-ligand lipoprotein receptor, it is expressed throughout the body but is predominantly found in the liver and steroidogenic tissue (161). It resides at the plasma membrane, with two transmembrane domains separated by a large extracellular region responsible for ligand binding (161). Its functions are varied and will be covered in more detail in a later section. However its major role within the liver is the uptake of cholesterol from high
29 density lipoprotein (HDL), allowing selective sorting and if necessary excretion into the bile (161, 286). Identification of SR-BI as a HCV co-receptor also relied on recombinant viral glycoproteins. Scarselli et. al. noted that sE2 bound to CD81 negative HepG2 cells, indicating another means of attachment (274). sE2 pull down of biotinylated HepG2 cell surface molecules, isolated an 82kDa glycoprotein found to be SR-BI. To confirm this Chinese hamster ovary (CHO) cells were transfected to express human SR-BI and were found to bind HCV sE2 (274). E2-SR-BI interactions are currently believed to occur via HVR1, as deletion of this region and anti-HVR1 mAbs ablate sE2 binding to CHO SR-BI cells (26, 274). HCVpp virus lacking the HVR ("HVR) are poorly infectious (25), however it has been shown that "HVR HCV RNA is still infectious when inoculated in Chimpanzees, although this was accompanied with the rapid occurrence of adaptive mutations within the envelope proteins (104). Maillard et. al. reported that patient serum derived HCV may interact with SR-BI via particle associated lipoproteins and this may provide an explanation for why "HVR HCV is still infectious (190). The major SR-BI ligand HDL enhances HCVpp and HCVcc infection (80, 325), although not all HCV genotypes respond to treatment (326). This phenotype is dependent on HVR1 interaction(s) with SR-BI and on the ability of SR-BI to transfer cholesterol from lipoproteins (25, 80, 324, 325). The mechanism by which this occurs is still unclear, however it is thought to
Page 1 and 2: The role of scavenger receptor B-I
Page 3 and 4: i Abstract. With 170 million infect
Page 5 and 6: iii Acknowledgements. I would like
Page 7 and 8: v 5 Results: Identification of a re
Page 9 and 10: vii Figure 5-5 Analysis of JFH-1 wt
Page 11 and 12: 1 Introduction 1.1 The disease. 1 D
Page 13 and 14: 3 predominantly immuno-pathogenic i
Page 15 and 16: 5 Aside from considerations of the
Page 17 and 18: 7 Current attempts to design a HCV
Page 19 and 20: 1.2 An elusive pathogen. 9 The emer
Page 21 and 22: 11 PCR). This technique is highly s
Page 23 and 24: 13 Within six years of the descript
Page 25 and 26: 1.3 Basic virology. 15 Like other m
Page 27 and 28: 17 Figure 1-2 HCV genome and polypr
Page 29 and 30: 19 241). E1 and E2 are anchored to
Page 31 and 32: 21 The characterisation of HCV geno
Page 33 and 34: 23 in the E1 and E2 glycoprotein ge
Page 35 and 36: 25 The solution reached by a great
Page 37: 27 binding to mouse cells. sE2 inte
Page 41 and 42: 31 blood brain barrier is permeable
Page 43 and 44: 33 act as receptors for viral entry
Page 45 and 46: 1.4.2 Attachment factors 35 The tru
Page 47 and 48: 1.4.3 Endocytosis and fusion 37 Aft
Page 49 and 50: 39 1.4.4 Co-receptor interplay and
Page 51 and 52: 41 inhibition of protein kinase A (
Page 53 and 54: 1.5 Lipoproteins 43 Since 1992 ther
Page 55 and 56: 45 Lipoproteins exist in a dynamic
Page 57 and 58: 47 and delivers its cargo via the w
Page 59 and 60: 49 uptake of cholesterol from LDL (
Page 61 and 62: Figure 1-4 SR-BI-lipoprotein intera
Page 63 and 64: 53 In summary the class B scavenger
Page 65 and 66: 55 In 1992 Thomssen et. al. demonst
Page 67 and 68: 57 lipoprotein association promotes
Page 69 and 70: 59 Figure 1-5 Lipo-viro-particle as
Page 71 and 72: 61 In vitro culture medium, into wh
Page 73 and 74: 2 Materials and methods. 2.1 Cell l
Page 75 and 76: Preparation of rat anti-E2 mAbs. 65
Page 77 and 78: 2.4 Basic techniques. Flow cytometr
Page 79 and 80: 69 6. Finally, the cells were washe
Page 81 and 82: 71 (Promega, WI, USA) kits accordin
Page 83 and 84: 73 proteins and are incapable of fu
Page 85 and 86: 75 spectrophotometer (Amersham), we
Page 87 and 88: 77 Figure 2-2 Electroporated Huh-7.
Page 89 and 90:
79 5. Data is expressed as percenta
Page 91 and 92:
81 (Invitrogen). The samples to be
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83 1. The SR-BII coding region was
Page 95 and 96:
2.7 Cloning and synthesis of JFH-1
Page 97 and 98:
The sequence encoding amino acids 3
Page 99 and 100:
Figure 2-6 sE2 sequencing. 89 JFH-1
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91 7. Large scale transfections wer
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93 3 Results: Investigations using
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95 3.2 CHO cells expressing human S
Page 107 and 108:
Figure 3-3 Ability of anti-E2 mAb t
Page 109 and 110:
99 3.3 The interaction of sE2 with
Page 111 and 112:
101 Figure 3-5 Position of SR-BI mu
Page 113 and 114:
103 Table 3-2 Investigation of cell
Page 115 and 116:
105 3.4 Expression of SR-BII in CHO
Page 117 and 118:
3.5 Discussion. 107 We have demonst
Page 119 and 120:
109 may offer a tool to study the i
Page 121 and 122:
111 Figure 4-1A displays endogenous
Page 123 and 124:
113 4.2 Exogenous expression of SR-
Page 125 and 126:
115 4.3 Evidence of enhanced JFH-1
Page 127 and 128:
117 4.4 SR-BI expression levels lim
Page 129 and 130:
119 4.5 Murine SR-BI does not enhan
Page 131 and 132:
121 4.6 SR-BI/II expression levels
Page 133 and 134:
123 Figure 4-5 Over expression of S
Page 135 and 136:
125 Figure 4-6 Anti-SR-BI serum inh
Page 137 and 138:
127 Figure 4-7 Infection of Huh-7.5
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129 cells is largely manifested in
Page 141 and 142:
131 5 Results: Identification of a
Page 143 and 144:
133 Figure 5-1 JFH-1 G451R has an a
Page 145 and 146:
135 Figure 5-2 CD81 dependence of J
Page 147 and 148:
137 G451R sE2 with hCD81 LEL we com
Page 149 and 150:
139 Figure 5-4 JFH-1 wt and G451R s
Page 151 and 152:
141 demonstrated a lower dependence
Page 153 and 154:
143 Figure 5-6 Relationship between
Page 155 and 156:
145 flow cytometry (data not shown)
Page 157 and 158:
147 5.6 Low density JFH-1 particles
Page 159 and 160:
5.7 Discussion. 149 We have demonst
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151 Numerous reports have used dens
Page 163 and 164:
153 demonstrate that low density JF
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155 to over express SR-BI we were a
Page 167 and 168:
157 5-1), better able to engage CD8
Page 169 and 170:
159 Figure 6-1 An overview of antib
Page 171 and 172:
161 it is believed that ligation of
Page 173 and 174:
163 Given our and other’s finding
Page 175 and 176:
6.3 HCV lipo-viro-particles. 165 As
Page 177 and 178:
167 represent the hyper-variable re
Page 179 and 180:
169 The G451R mutation disrupts the
Page 181 and 182:
7 Bibliography 171 1. Acton, S., D.
Page 183 and 184:
173 include the CD81 tetraspanin an
Page 185 and 186:
175 receptor class B type I and inh
Page 187 and 188:
177 83. Drummer, H. E., K. A. Wilso
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179 KewalRamani, D. R. Littman, C.
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181 King. 1996. Efficient infection
Page 193 and 194:
183 hepatitis C virus envelope glyc
Page 195 and 196:
185 recovered chimpanzees exhibit r
Page 197 and 198:
187 218. Monazahian, M., I. Bohme,
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189 243. Perez-Berna, A. J., J. Gui
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191 single-cycle production assay t
Page 203 and 204:
193 298. Strickland, G. T., S. S. E
Page 205 and 206:
195 Remaley, G. Csako, T. L. Eggerm
Page 207:
197 2007. Scavenger receptor class
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