ライフサイエンスコーパス: tapasin

1 f peptide editing by TAPBPR and, by analogy, tapasin.

2 g site and the glycan of the assembly factor tapasin.

3 ticulin, the thiol oxidoreductase ERp57, and tapasin.

4 mponents low-m.w. protein 2, TAP1, TAP2, and tapasin.

5 lation of the APM components TAP1, TAP2, and tapasin.

6 of action for the peptide-exchange chaperone tapasin.

7 ly optimal to allow MHC class I release from tapasin.

8 y in vitro upon mixing recombinant ERp57 and tapasin.

9 in of ERp57 to maintain its interaction with tapasin.

10 defining a requirement for interaction with tapasin.

11 in-assembled HLA-B8 molecules than wild-type tapasin.

12 le endoplasmic reticulum proteins, including tapasin.

13 ith the proposed peptide-editing function of tapasin.

14 n L(d) and mouse tapasin compared with human tapasin.

15 elic haplotypes at 25 loci between HLA-A and Tapasin.

16 association with TAP, as reported for native tapasin.

17 TAP subunits is observed in the presence of tapasin.

18 peptide-loading complex (PLC) by recruiting tapasin.

19 TAP1 and TAP2 as well as avian TAP2 recruits tapasin.

20 m the structural similarities of TAPBPR with tapasin.

21 n the MHC alleles in their interactions with tapasin.

22 d absence of a recombinant truncated form of tapasin.

23 One of these accessory molecules is tapasin, a transmembrane protein that tethers empty clas

24 inant-negative perhaps by blocking wild-type tapasin access to TAP.

25 Instead, we propose that tapasin acts as a peptide facilitator.

26 We propose that tapasin acts primarily to increase efficiency of assembl

27 found that substitutions at position K408 in tapasin affected the expression of MHC class I molecules

28 Tapasin alleles contribute to the outcome of HCV infecti

29 b) complexes formed in the absence of TAP or tapasin, although not as efficiently as in wild-type cel

30 ng for proteasome catalytic proteins and for tapasin, an endoplasmic reticulum resident protein invol

31 We recently found that tapasin, an important component of the LC, interacts wit

32 eticulin and the MHC class I assembly factor tapasin and are important for maintaining steady-state l

33 ectively, this supports the possibility that tapasin and BF2 proteins have co-evolved, resulting in a

34 ide linked to the class I-specific chaperone tapasin and CRT were the minimal PLC components required

35 We discuss here the dynamic interactions of tapasin and DM with their corresponding MHC molecules th

36 Tapasin and ERp57 have been shown to exist in the peptid

37 the protein crystal structure heterodimer of tapasin and ERp57, which helps visualize the function of

38 HLA-B locus at which heterozygosity of both tapasin and HLA-B was protective (P < 0.03).

39 The accessory proteins tapasin and HLA-DM (DM) crucially influence the selectio

40 ss I molecules to alter the requirements for tapasin and incorporation into the peptide loading compl

41 ous pathway by its independence from TAP and tapasin and its sensitivity to inhibitors of lysosomal e

42 st, we show that a mismatched combination of tapasin and MHC alleles exhibit significantly impaired M

43 for maintaining steady-state levels of both tapasin and MHC class I heavy chains.

44 pecific way, via the co-evolution of chicken tapasin and MHC I.

45 er, at near physiological temperatures, both tapasin and nucleotides stabilize the peptide binding si

46 These defects include loss of tapasin and one HLA haplotype as well as selective silen

47 Thus, tapasin and TAP are required for MHC-I to bind ER-derive

48 In addition, we found that tapasin and TAP were not involved in FcRn assembly, as s

49 cupancy, which in turn determines binding to tapasin and TAP.

50 re two MHC class I specific peptide editors, tapasin and TAPBPR, intimately involved in controlling p

51 to map the sites of mK3 interaction with TAP/tapasin and to determine the requirements for substrate

52 ities of HLA-A*0201-associated peptides from tapasin(+) and tapasin(-) cells were equivalent, althoug

53 Tapasin(-/-) and TAP1(-/-) macrophages had decreased MHC

54 g in tapasin(-/-) cells and experiments with tapasin(-/-) and TAP1(-/-) macrophages that characterize

55 nate MHC-I processing was diminished in both tapasin(-/-) and TAP1(-/-) macrophages.

56 nsporter associated with antigen processing, tapasin, and beta(2)-microglobulin.

57 ated with Ag processing (TAP), calreticulin, tapasin, and ERp57.

58 both allotypes bound efficiently to TAP and tapasin, and furthermore, random nonamer peptides confer

59 fide with the MHC class I-specific chaperone tapasin, and this dimeric conjugate edits the peptide re

60 ponents of the MHCI peptide loading complex, tapasin, and transporter associated with antigen process

61 d distal to several classical MHC I loci, so tapasin appears to function in a universal way to assist

62 Here we show that ERp57 and tapasin are disulfide linked inside the loading complex.

63 These data are inconsistent with a role for tapasin as a peptide editor.

64 ns were impaired for tapasin-independent and tapasin-assisted assembly.

65 Therefore, tapasin-assisted loading of MHC I in chickens may occur

66 t self-loading is negatively correlated with tapasin-assisted loading.

67 of mK3 resulted in the ubiquitination of TAP/tapasin-associated class I, and mutants of class I incap

68 Ig-like domain, we demonstrated that H-2L(d)/tapasin association can be segregated from reconstitutio

69 Thus, tapasin association specifically inhibits the escape pat

70 this sequence abrogate human, but not mouse, tapasin association with L(d).

71 or differences in the expression patterns in tapasin(-/-) background suggest cell specificity in clas

72 together, the data indicate that TAPBPR and tapasin bind in a similar orientation to the same face o

73 Three tapasin binding sites on TAP have been described, two of

74 We show tapasin binding to both TAP1 and TAP2 and to the corresp

75 results obtained using TAP mutants that lack tapasin binding to either N-terminal domain, we conclude

76 In particular, the role of tapasin binding to the core TM domain of TAP1 single cha

77 -terminal domain, we conclude that all three tapasin-binding sites in TAP cooperate to achieve high t

78 in not only abolishes formation of the ERp57-tapasin bond but also prevents complete oxidation of the

79 hat presented in the presence of full-length tapasin, but the HLA-B8 molecules showed altered cell su

80 ociated with the peptide loading complex TAP/tapasin/calreticulin.

81 ompatibility complex (MHC) class I chaperone tapasin can be detected as a mixed disulfide with the th

82 ated under the peptide-binding platform that tapasin, CD8, and natural killer (NK)-receptors engage.

83 0201-associated peptides from tapasin(+) and tapasin(-) cells were equivalent, although steady state

84 monstrated reduced cell surface stability on tapasin(-) cells.

85 loading with high affinity peptides, whereas tapasin(-/-) cells allow poorly loaded MHC-I molecules t

86 st study of alternate MHC-I Ag processing in tapasin(-/-) cells and experiments with tapasin(-/-) and

87 at a large proportion of post-Golgi MHC-I on tapasin(-/-) cells might be peptide-receptive, enhancing

88 a indicate that CRT in the PLC enhances weak tapasin/class I interactions in a manner that is glycan-

89 gher overall affinity between L(d) and mouse tapasin compared with human tapasin.

90 We created three fluorescent tapasin constructs: wild-type tapasin, soluble tapasin,

91 d little or no expression of LMP2, TAP1, and tapasin, critical components of the HLA class I antigen-

92 2)m heterodimers, for which tapasin-ERp57 or tapasin-CRT complexes were not required.

93 However, tapasin deficiency significantly impaired the positive s

94 with this, cell surface HLA-B8 molecules in tapasin-deficient cells were less stable and the peptide

95 mK3 failed to regulate class I in TAP- or tapasin-deficient cells, and mK3 interacted with TAP/tap

96 Therefore, in this model, tapasin-deficient mice do not have a reduced but rather

97 f the alteration of the T cell repertoire in tapasin-deficient mice, because bone marrow chimeric mic

98 cant amounts of M3 are retained in the ER in tapasin-deficient mice, even in the presence of N-formyl

99 In tapasin-deficient mice, responses to subdominant fast of

100 P-1 cells and IgG-binding assays in 721.220 (tapasin-deficient) and 721.174 (TAP-deficient) cells tra

101 We found that tapasin Delta334-342 was unable to bind to the L(d) H ch

102 Although both peptide length and tapasin dependence are known to be important for HLA-I p

103 differences in substrate specificity and TAP/tapasin dependence between mK3 and kK5 permitted us, usi

104 LA-B*4402 is likely to underlie its stronger tapasin dependence for cell surface expression and therm

105 , while an Endo H-resistant form was clearly tapasin dependent.

106 emble more readily with peptides compared to tapasin-dependent allotypes that belong to the same supe

107 riable, with frequent occurrence of strongly tapasin-dependent or independent allotypes.

108 -I allomorphs are differentially affected by tapasin, different lengths of peptides generated differe

109 tion interface between TAP1 and TAP2 and the tapasin docking sites for PLC assembly are conserved in

110 Soluble tapasin does not increase MHC I surface levels to the sa

111 BPR, the interaction between MHC class I and tapasin does not increase.

112 CD8(+) T cell hierarchy was a consequence of tapasin editing and not a consequence of the alteration

113 Tapasin editing is therefore a contributing factor to th

114 Tapasin edits the peptide repertoire presented to CD8(+)

115 process was found to be dependent on TAP and tapasin, endoplasmic reticulum molecules involved in cla

116 re, the ERp57 binding site and the glycan of tapasin enhance beta(2)m and MHC class I heavy (H) chain

117 chain, beta(2)-microglobulin, calreticulin, tapasin, Erp57 (ER60) and the transporter associated wit

118 The rate of tapasin-ERp57 conjugate formation is unaffected by the a

119 Thus, the tapasin-ERp57 conjugate is the functional unit of the pe

120 al domains or a combinatorial feature of the tapasin-ERp57 conjugate.

121 nd facilitating peptide binding, recombinant tapasin-ERp57 conjugates accomplished both of those func

122 resent the 2.6 A resolution structure of the tapasin-ERp57 core of the PLC.

123 peptide loading and editing functions of the tapasin-ERp57 heterodimer.

124 of H chain-beta(2)m heterodimers, for which tapasin-ERp57 or tapasin-CRT complexes were not required

125 By combining the tapasin-ERp57 structure with those of other defined PLC

126 deficient cells, and mK3 interacted with TAP/tapasin, even in the absence of class I.

127 sin K408A-expressing cells than in wild-type tapasin-expressing cells.

128 In sharp contrast, tapasin expression was dispensable for the presentation

129 The conserved MHC class I glycan and tapasin facilitated an early step in the assembly of H c

130 -1b to the TAP peptide transporter, and that tapasin facilitates the delivery of Qa-1b molecules to t

131 that the correlation between high degree of tapasin facilitation and low stability is valid for diff

132 We also demonstrate that tapasin facilitation varies for different peptide length

133 sence of tapasin; furthermore, dependence on tapasin for cell surface expression did not correlate wi

134 ss I and are critically dependent on TAP and tapasin for display of surface Ags.

135 We have evaluated the role of tapasin for the assembly of peptides with the class Ib m

136 tapasin position 408 increased the amount of tapasin found in association with the open, peptide-free

137 main thought to bind tapasin influenced both tapasin function and intrinsic peptide binding propertie

138 that proximity to TAP is necessary for full tapasin function.

139 tical role for the tapasin Ig-like domain in tapasin function.

140 trating that proteasomes, as well as TAP and tapasin, functioned normally.

141 ecules depends on the chaperone tapasin; how tapasin functions is not fully understood.

142 peptide acquisition by L(d) is influenced by tapasin functions that are independent of L(d) binding.

143 The co-factor tapasin functions to ensure that MHC I becomes loaded wi

144 s were expressed optimally in the absence of tapasin; furthermore, dependence on tapasin for cell sur

145 ele with an aspartate at residue 114 and the tapasin G allele also had stronger CD8+ T-cell responses

146 ean, but not a US, Caucasian population, the tapasin G allele was significantly associated with the o

147 ele with an aspartate at residue 114 and the tapasin G allele were more likely to spontaneously resol

148 In most mammals, the tapasin gene appears to have little sequence diversity a

149 In contrast, the chicken tapasin gene is tightly linked to the single dominantly

150 own G/C coding polymorphism in exon 4 of the tapasin gene.

151 roglobulin, as well as normal levels of TAP, tapasin, GRP78, calnexin, calreticulin, ERp57, and prote

152 Tapasin has been proposed to function as a peptide edito

153 In conclusion, these data show that tapasin has specificity for the combination of peptide l

154 rotein, related (TAPBPR), a widely expressed tapasin homolog, is not part of the classical MHC-I pept

155 itor TAPBPR (TAP-binding protein-related), a tapasin homolog.

156 of MHC I molecules depends on the chaperone tapasin; how tapasin functions is not fully understood.

157 er point mutations in the same region of the tapasin Ig-like domain affect MHC class I surface expres

158 these results reveal a critical role for the tapasin Ig-like domain in tapasin function.

159 studying the effects of substitutions in the tapasin Ig-like domain, we demonstrated that H-2L(d)/tap

160 s, previous data determining the function of tapasin in the MHC class I Ag-processing and presentatio

161 The functions ascribed to tapasin include: 1) ER retention of peptide-empty class

162 tapasin might explain the observations that tapasin increases TAP protein expression levels in mamma

163 hicken are fixed in duck alleles and suggest tapasin independence.

164 ndings that some HLA-B allotypes shown to be tapasin independent are associated with rapid progressio

165 orms expressed, an Endo H-sensitive form was tapasin independent, while an Endo H-resistant form was

166 In vitro refolded forms of tapasin-independent allotypes assemble more readily with

167 nd, during refolding, reduced aggregation of tapasin-independent allotypes is observed.

168 glycan-deficient H chains were impaired for tapasin-independent and tapasin-assisted assembly.

169 l end of the peptide are key determinants of tapasin-independent assembly.

170 ically, in HIV-infected individuals, greater tapasin-independent HLA-B assembly confers more rapid pr

171 s downregulate human B7.2 molecules in a TAP/tapasin-independent manner.

172 polymorphic MHC residues thought to contact tapasin influence maturation efficiency.

173 e cysteine residues in the Ig-like domain of tapasin influence tapasin's stability, its interaction w

174 e in the MHC I alpha3 domain thought to bind tapasin influenced both tapasin function and intrinsic p

175 igated the mechanisms by which the co-factor tapasin influences MHC I plasticity.

176 Evidence also has been presented that tapasin influences the loading of peptides onto MHC clas

177 Tapasin influences the quantity and quality of MHC/pepti

178 s I, and mutants of class I incapable of TAP/tapasin interaction were unaffected by mK3.

179 Here we investigated TAP-tapasin interactions and their effects on TAP function i

180 However, tapasin interactions with either the truncated TAP const

181 The structure revealed that tapasin interacts with both ERp57 catalytic domains, acc

182 hat influence peptide-loading properties and tapasin involvement in chicken are fixed in duck alleles

183 Tapasin is a glycoprotein critical for loading major his

184 in which the MHC class I-dedicated chaperone tapasin is a key player.

185 Assuming tapasin is a prolate ellipsoid, we calculated an apparen

186 Tapasin is a type I membrane glycoprotein involved with

187 Here we show that tapasin is a unique and preferred substrate, a substanti

188 Tapasin is an endoplasmic reticulum resident protein tha

189 s to permit detection of infected cells, and tapasin is an important component of the peptide loading

190 Tapasin is an integral component of the peptide-loading

191 Collectively, these results suggest that tapasin is comprised of two core domains of different si

192 ulin peptides onto Qa-1b molecules, and that tapasin is dispensable for retention of empty Qa-1b mole

193 Chicken tapasin is highly polymorphic, but co-evolution with TAP

194 articular, dependence on the assembly factor tapasin is highly variable, with frequent occurrence of

195 Sedimentation analysis showed that tapasin is monomeric in solution with a sedimentation co

196 e endoplasmic reticulum (ER), though soluble tapasin is more mobile than wild type and N300.

197 al cell surface expression in the absence of tapasin is not a prerequisite for susceptibility to AS.

198 Tapasin is not required for high affinity peptide bindin

199 gion in the Ig-like domain of mouse or human tapasin is required for association with L(d), and certa

200 Tapasin is required to promote TAP stability, but throug

201 molecular mechanism of this process and how tapasin itself is retained in the ER are unknown.

202 Tapasin K408A was also associated with more folded, beta

203 tent with our observation of a large pool of tapasin K408A-associated HLA-B8 molecules, the rate at w

204 from the endoplasmic reticulum was slower in tapasin K408A-expressing cells than in wild-type tapasin

205 ice (wild-type recipients reconstituted with tapasin knockout bone marrow) showed the same hierarchy

206 Although tapasin knockout cells have low MHC I surface expression

207 one marrow) showed the same hierarchy as the tapasin knockout mice.

208 Our results show that tapasin links Qa-1b to the TAP peptide transporter, and

209 Tapasin loss is caused by a germ-line frameshift mutatio

210 the alanine substitution at position 408 in tapasin may interfere with the stable acquisition by MHC

211 Repression of ERAP1, TAPASIN, MECL1, and LMP7 by PRDM1 results in failure to

212 t a role for disulfide bond isomerization in tapasin-mediated peptide loading.

213 that, in addition to the extensively studied tapasin-mediated quality control mechanism, UGT1 adds a

214 Because tapasin, MHC class I, and TAP are transmembrane proteins

215 We also report that the tapasin/MHC I ratio varies, with the PLC population comp

216 ty of TAP1.TAP2 complexes in the presence of tapasin might explain the observations that tapasin incr

217 We propose that tapasin modulates MHC I plasticity by dynamically coupli

218 -F surface expression for functional TAP and tapasin molecules and identified a clear departure from

219 Almost all tapasin molecules were clustered, and these clusters dif

220 YFP-tapasin molecules were functional and could be isolated

221 tate class I assembly, we have created novel tapasin mutants and expressed them in 721.220-L(d) cells

222 lls unable to form the conjugate, because of tapasin mutation in human studies or ERp57 deletion in m

223 ous enzymes revealed that a narrow region of tapasin near residue 90 is highly susceptible to digesti

224 ability of ER resident MHC I is decreased in tapasin-negative cells.

225 Mutagenesis of cysteine 95 in tapasin not only abolishes formation of the ERp57-tapasi

226 e compared TAP function and interaction with tapasin of a range of species within two classes of jawe

227 Tapasin oligomers appear to be retained by the failure o

228 To investigate the role of tapasin on T cell immunodominance we used poxvirus viral

229 reactive dimers accumulate in the absence of tapasin or beta(2)-microglobulin, whereas W6/32-reactive

230 Incubation of tapasin(-/-) or TAP1(-/-) cells at 26 degrees C decrease

231 ) association, using cell lines lacking TAP, tapasin, or beta(2)m.

232 ex, an oligomeric complex that the chaperone tapasin organizes by bridging TAP to MHC class I and rec

233 idase associated with Ag processing, but not tapasin, partially destroyed or removed cytoplasmic clas

234 These findings reveal that tapasin plays a differential role in the loading of Qdm

235 We sought to determine if tapasin polymorphisms affected the outcome of HCV infect

236 anine, but not tryptophan, for the lysine at tapasin position 408 increased the amount of tapasin fou

237 UV circular dichroism spectrum revealed that tapasin possesses well-defined secondary structural elem

238 length and HLA-I allomorph, and suggest that tapasin promotes formation of pHLA-I complexes with high

239 Tapasin promotes retention of MHC-I in the endoplasmic r

240 with respect to class I, mK3 binding to TAP/tapasin, rather than the presence of unique sequences in

241 cule pulldown (SiMPull), we determined a TAP/tapasin ratio of 1:2, consistent with previous studies o

242 This treatment combined with tapasin reconstitution and IFN-gamma stimulation restore

243 We recently identified a tapasin-related molecule, TAPBPR, as an additional compo

244 en enhanced with the identification that the tapasin-related protein TAPBPR is a second major histoco

245 We investigated the function of the tapasin-related protein, TAPBPR.

246 nal structure of the lumenal region of human tapasin (residues 1-392) tagged with a (His)(6) sequence

247 Here, evidence is presented that tapasin retains class I molecules in the ER until they a

248 Tapasin retains empty or suboptimally loaded MHC class I

249 Mutagenesis of these cysteines decreases tapasin's electrophoretic mobility, suggesting that thes

250 s in the Ig-like domain of tapasin influence tapasin's stability, its interaction with the MHC class

251 TAP2 complexes, and in fact, the presence of tapasin slightly reduces the affinity of TAP complexes f

252 ee fluorescent tapasin constructs: wild-type tapasin, soluble tapasin, which does not interact with T

253 ules at the cell surface, and down-regulated tapasin stabilization of TAP.

254 MHC class I crucial for its association with tapasin, such as T134, are also essential for its intera

255 endoplasmic reticulum retention and enhanced tapasin-TAP binding.

256 *4405 to acquire peptides without binding to tapasin-TAP complexes.

257 5 is not inherently unable to associate with tapasin-TAP complexes.

258 alreticulin, protein disulfide isomerase A3, tapasin, TAP1, and TAP2.

259 We sought to determine whether, like tapasin, TAPBPR can also influence MHC class I peptide s

260 In contrast to tapasin, TAPBPR does not bind ERp57 or calreticulin and

261 Like tapasin, TAPBPR is widely expressed, IFN-gamma-inducible

262 , CD40, CCR7 as well as LMP2, TAP1, TAP2 and tapasin than conv. mix-matured DC.

263 expression of MB1, LMP-7, LMP-10, TAP-1, and tapasin than mature DC.

264 eticulum, the transmembrane proteins TAP and tapasin that facilitate peptide binding to MHCI proteins

265 l analysis identified a conserved surface on tapasin that interacted with MHC class I molecules and w

266 the MHC class I assembly machinery, TAP and tapasin, that are required for mK3 function.

267 In the absence of tapasin, the association of MHC class I with TAPBPR is i

268 associated with antigen processing (TAP) and tapasin, the endoplasmic reticulum (ER) oxido-reductases

269 n addition to affecting TAP interaction with tapasin, the substitution of alanine, but not tryptophan

270 Full-length tapasin then confers additional stability on class I MHC

271 class I molecules and their assembly factor tapasin, thereby influencing antigen presentation to cyt

272 lore the relationship between the ability of tapasin to bind to TAP and the MHC class I H chain and t

273 alitatively and quantitatively influenced by tapasin to different degrees, but again, its effect has

274 In this review, we use recent studies of tapasin to examine the efficiency of TAP, the LC constit

275 d the MHC class I H chain and the ability of tapasin to facilitate class I assembly, we have created

276 w that the amino acid residues important for tapasin to interact with MHC class I are highly conserve

277 Thus, mK3 subverts TAP/tapasin to specifically target class I molecules for des

278 Tapasin (Tpn) has been implicated in multiple steps of t

279 the peptide-loading complex (PLC), to which tapasin (TPN) recruits MHC class I (MHC I) and accessory

280 In this article, we show that both tapasin (Tpn), a key component of the peptide loading co

281 Tapasin (tpn), an essential component of the MHC class I

282 We examined interactions in a soluble tapasin (TPN)/HLA-B*0801 complex to gain mechanistic ins

283 ed lysine at position 408, which lies in the tapasin transmembrane/cytoplasmic domain.

284 s I, and TAP are transmembrane proteins, the tapasin transmembrane/cytoplasmic region has the potenti

285 rticle, we delineate the interaction between tapasin (Tsn) and MHC I molecules.

286 Tapasin upregulation by interferon-gamma induces sequest

287 Tapasin was also required for the presentation of endoge

288 YFP-tapasin was excluded from ER exit sites even after accum

289 em, we demonstrate that although recombinant tapasin was ineffective in recruiting MHC class I molecu

290 ide repertoire from cells expressing soluble tapasin was similar in both appearance and affinity to t

291 Cell lines with nonfunctional tapasin were transiently transfected with different B27

292 ties of peptides expressed in the absence of tapasin were unexpectedly higher, not lower.

293 NPs) in 5 genes (LMP2, TAP1, LMP7, TAP2, and Tapasin) were investigated for association with suscepti

294 lease peptides in the presence or absence of tapasin, where, as in mammals, efficient self-loading is

295 eins, including TAP-associated glycoprotein (tapasin), which tethers empty MHC class I molecules to t

296 , which does not interact with TAP, and N300 tapasin, which does not interact with MHC I.

297 pasin constructs: wild-type tapasin, soluble tapasin, which does not interact with TAP, and N300 tapa

298 d with antigen processing (TAP) and MHC I to tapasin, which is responsible for MHC I recruitment and

299 These questions were addressed by tagging tapasin with the cyan fluorescent protein or yellow fluo

300 MHC I in a peptide-receptive state and, like tapasin, works to enhance peptide optimisation.