Overview of the Unfolded Protein Response
13th International Myeloma Workshop
632011
AnnHwee Lee, PhD
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Harvard Medical School/School of Public
Health
Hallmark feature of plasma cell differentiation
Resting B cell
Active B cell
(Plasma cell)
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Maturation of secretory and
transmembrane proteins
Lipid membrane biogenesis
Major calcium storage
UPR is activated by ER stress
Tunicamycin
Grp78
· Pharmacological
Tunicamycin, DTT, etc
Grp94
· Physiological
Secretory proteins (Immunoglobulins)
CHOP
ER stress ·Pathological
Misfolded proteins
RNA
UPR
Apoptosis Degradation
Transport
Folding
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UPR signaling pathway Saccharomyces cerevisiae
DTT
PI
Inositol
SS
INO1
SH
SH
G6P
IRE1
UDPGlcNAc
Tunicamycin
Thapsigargin
Ca++
HAC1
BiP (Kar2p)
Protein folding
UPRE
INO1
Phospholipid biosynthesis
IRE1 : Nikawa J, Yamashita and S, Mol Microbiol., 1992
Mori K and J. Sambrook J, Cell, 1993
HAC1 : Cox J and Walter P, Cell, 1993
Mammalian UPR signaling pathway
PERK IRE1 ATF6
P
Proteolytic
eIF2
XBP1 mRNA
processing
Suppress
Protein
synthesis
ATF4
XBP1(S)
ATF6(N)
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IRE1/XBP1 signaling pathway
Unfolded protein species
BiP
Luminal
ER membrane
P
P
IRE1
Cytosolic
Unfolded protein species
P
P
IRE1
Credle et al., Proc. Natl. Acad. Sci. USA. 2005
Zhou et al., Proc. Natl. Acad. Sci. USA. 2006
Lee et al., Cell. 2008
Korennykh, et al., Nature. 2009
Ali et al., EMBO 2011
IRE1/XBP1 signaling pathway
IRE1
Luminal
P
P
ER membrane
Cytosolic
Kinase
XBP1 mRNA
Endoribonuclease
XBP1s
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Splicing of XBP1 mRNA by IRE1
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XBP1s
XBP1 is highly expressed in secretory organs
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BIOGPS : http://biogps.gnf.org/
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Role of XBP1 in development of secretory cells
Plasma cell
Pancreatic acinar cell
Paneth cell
Reimold et al, Nature, 2001
Lee et al, EMBO 2005
Kaser et al, Cell 2008
Severely impaired plasma cell generation in the
absence of XBP1 and greatly diminished
immunoglobulin
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Induction and IRE1mediated splicing of XBP1
mRNA during plasma cell differentiation
LPS stimulation
Time (h):
0
244872
XBP1
actin
forward
26bp
XBP-1u
XBP-1s
reverse
XBP1s
Iwakoshi et al. Nat. Immunol. (2003)
Impaired immunoglobulin production from XBP1
deficient B cells
ES cells
XBP1-/-
Blastocyst
Rag2-/-
Lymphoid cells : XBP1-/-
Liver : Rag2-/-
Others : Mixture of Rag2-/- and XBP1-/-
Reimold et al., Nature, 2001
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XBP1/ Rag chimeras fail to mount an
immune response
Reimold et al., Nature, 2001
UPR activation during plasma cell differentiation
PERK
IRE1
ATF6
ER
Block
P
eIF2
Protein
synthesis
ATF4
XBP1(S)
ATF6(N)
CHOP
Ma et al., Cell Stress and Chaperones (2010) 15:281­293
Gass et al., Molecular Immunology 45 (2008) 1035­1043
Gass et al., J Biol Chem 277 (2002) 49047­49054
Zhang et al., J Clin Invest. 115 (2005 ) 268­281
Iwakoshi et al. Nat. Immunol. 4 (2003) 321329
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XBP1 is essential for the development of
pancreatic acinar cells
WT
Xbp1/
LivXBP1
500 nm
500 nm
Lee et al. EMBO (2005)
XBP1 induces ER expansion and activates genes in protein
secretory pathway
XBP1
Phospholipid
Secretory Pathway
Synthesis
ER expansion
Translocation
Degradation
Sec61
EDEM
Derl1
Herp
Hrd1
Control
XBP1s
Mannosidase I
Folding
ERdj3
Grp78
p58IPK
Grp94
ERdj4
PDIs
Lee et al Mol. Cell. Biol. 2003
Shaffer et al Immunity 2004
Shaffer et al Immunity 2004
Sriburi et al J. Cell Biol 2004
Acosta-Alvear et al Mol. Cell 2007
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Critical function of XBP1 in biogenesis
of cellular secretory machinery
Translocation
P
P
IRE1
Folding
Ig
Secretion
Zymogen
Degradation
XBP1 mRNA
ER expansion
XBP1s
Transcription
Is XBP1 also required for the survival of
myeloma cells?
What is the role of XBP1 in myeloma cells
treated with proteasome inhibitors
(Velcade)?
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Proteasome inhibitors target IRE1/XBP1
· Inhibit IRE1 driven XBP1 mRNA splicing
· Stabilize XBP1u protein that acts as a dominant negative
stin
MG132 (1 µM)
132
acy
341
0124
8
16 hr
MG
PS
Lact
Tm :

+
++
+
XBP1s
XBP1u
XBP1s
XBP1u
Lee et al. PNAS (2003)
Inhibition of IRE1/XBP1 by proteasome inhibitors
correlates with apoptosis of myeloma cells
PI
90
ER stress
80
70
(%)
60
th
50
XBP1
40
l Dea
30
Cel
20
10
Protection
0
0
1
248 16 hr
MG132 (1 µM)
Apoptosis
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Does XBP1 have a protective role in human
diseases associated with aggregation of
misfolded proteins?
Diseases associated with protein misfolding in the ER
Export
Degradation
Aggregation
No functional protein
Accumulation of misfolded protein
Cystic fibrosis
Alzheimer disease
Hereditary emphysema
Prion diseases
Hereditary hemochromatosis
Neonatal Diabetes
Duchenne muscular dystrophy
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XBP1 does not affect prion pathogenesis
Hetz C. et.al. PNAS 2008;105:757762
©2008 by National Academy of Sciences
Delayed Amyotrophic Lateral Sclerosis by XBP1
deletion in brain
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QuickTimeTM and a
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QuickTimeTM and a
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Hetz et al, Genes and Dev.(2010)
13

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Role of UPR in other organ system
·Liver lipid metabolism
·Dual roles of IRE1
Low plasma lipid levels in XBP1 mice
4 weeks after Xbp1 deletion (polyIC injection)
WT, n = 12
Xbp1, n = 14
Lee et al. Science (2008)
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Induction and hyperactivation of IRE1 by XBP1
deficiency in liver









1
1
1
1
1
1
1
1
1
p
p
p
p
p
p
p
p
p
WT
WT
WT
WT
Xb
Xb
Xb
Xb
Xb
WT
WT
WT
WT
Xb
Xb
Xb
Xb
phospho-IRE1
IRE1
Hsp90
7.5 µM PhosTag
Dual roles of IRE1/XBP1 UPR signaling in hepatic
lipid metabolism
IRE1
His.IRE1
His.IRE1
P
P
1
2
3
AAAA
AAAA
IRE1
AAAA
XBP1 mRNA
substrate
XBP1
mRNA
mRNA
RNA ligase
XBP1s
Ribonuclease
Splicing
Promote lipogenesis
Suppress lipogenesis
Degradation
15

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Physiological functions of the UPR
ER signaling
ER stress
TLR activation macrophage
Phamacological (Tunicamycin, DTT)
High glucose liver
Physiological ER stress (secretory protein, ?)
Feedbak regulation
PERK
IRE1
ATF6
UPR/Stress response Development
Lipogenesis
Inflammtion
Protein
ER expansion
Lipogenic
Cytokines
folding homeostasis
ER chaperones in
enzymes
secretory cells
Acknowledgements
Harvard School of Public Health
Harvard Medical School
Laurie H.Glimcher
Gerald C. Chu
Andreas Reimold
Huib Ovaa
Neal Iwakoshi
Boaz Tirosh
Claudio Hetz
Hidde Ploegh
Derrick Todd
Fabio Martinon
National Institute of Health
Art L. Shaffer
Brigham and Women's Hospital
Louis M. Staudt
David E. Cohen
Erez F Scapa
RIKEN
Richard Blumberg
Takao Iwawaki
Arther Kaser
DanaFarber Cancer Institute
Kenneth C. Anderson
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