Mutations in the COPA gene, which encodes a subunit of the COPI vesicle coat complex important for retrograde Golgi-ER transport, were found to cause a rare inherited autoimmune disease characterized by inflammatory lung disease and arthritis. The identified mutations impaired COPA's ability to bind cargo proteins for transport. Patient cells exhibited elevated endoplasmic reticulum (ER) stress and the expression of pro-inflammatory cytokines that promote a T helper 17 cell response. It is proposed that mutant COPA causes ER stress, which leads to immune activation and generation of Th17 cells driving the autoimmune phenotype. This identifies the first example of a vesicular trafficking defect causing autoimmunity and provides insights into molecular links between ER stress and

1. COPA mutations impair Golgi-ER transport
causing hereditary autoimmune-mediated
lung disease and arthritis
Tony Shum, MD
Assistant Professor
Pulmonary & Critical Care
Cardiovascular Research Institute
University of California San Francisco
shumlab.ucsf.edu

2. A patient with autoimmune-associated lung
and joint disease
• ID: 30 yo female with JIA, advanced ILD
• CC: coughing up blood
• PMH:
– JIA: Presented joint pain 2 yrs (knees, ankles, hands/fingers)
– ILD: soon developed shortness of breath, diagnosed ILD (follicular
bronchiolitis, lymphoid aggregates)
• FH: sister and deceased aunt with similar medical history
• SH: non-smoker
• ROS: achy joints, no URI symptoms but slight fever
• Exam:
– Hypoxemic, tachypneic
– Lungs with diffuse crackles
– Coughing up scant bright red blood

3. More Data:
• Representative CT • ANA neg
• CCP/RF neg
• MPO Ab – highly elevated
• Hand films – no erosions

4. A family with a rare disorder of autoimmune -
associated lung lung and joint disease
• Clinical Features:
• High-titer autoantibodies: ANCA, ANA
• Inflammatory arthritis and ILD
• Immunosuppression required (e.g. mycophenolate)

5. Genetic Linkage IDs a Single Region of
Significance on Chr 1
Noah Zaitlen
LOD=3.5
LOD score > 3.0 = 1000 to 1 odds that linkage did not occur by chance

6. WES IDs a single rare, non-synonymous variant under
Chr 1 linkage peak
• Missense mutation in COPA c.G721A:p.E241K
• Minor allele frequency: not reported (i.e. very
rare)
• Predicted crippling (AVSIFT, Polyphen)
• Sanger validated in > 15 subjects

7. Baylor-Hopkins Center for Mendelian Genomics
independently IDs COPA mutations in 2 families
with exact same clinical phenotype
A
B
U C S
F
L . F a
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C
B a y l o
r
B a y l o
r
U C S F
M . W a t e r f i e l d
D
E
T o r o n t o
( S . D e l l )

9. Patient autoantibodies

10. Immunoglobulin levels, absolute lymphocyte
counts and CD4 to CD8 cell ratios were normal

11. Lungs of unrelated patients reveals
germinal center formation &
infiltrating CD4 T cells

12. Immune-mediated kidney disease

13. 4 COPA mutations are discovered in 5 families
all located in highly conserved WD40 domain

14. Coatomer Subunit Alpha (COPA)
• Ubiquitously expressed
• Subunit of Coat Protein Complex I
(COPI)
• Enables protein transport between
the Golgi and ER
• No disease associations reported in
COPA or COPI
Brandizzi F and Barlow C Nat Rev Mol Cell Biol 2013

15. COPA expression & localization
appear normal in patients
c
CO – control
PA – patient

16. COPI is important for retrograde
transport of proteins
K K
X X
Adapted from Brandizzi F and Barlow C Nat Rev Mol Cell Biol 2013

17. The COPA WD40 domain is critical for
retrograde transport of KKXX proteins
Eugster A EMBO J 2000

18. Mutant COPA has impaired binding to
KKXX proteins
K K X
X*

20. ER stress and the UPR have been implicated
in autoimmunity & lung disease
• Lung disease
– Misfolded surfactant proteins leads to ER stress
and propensity to lung inflammation and
scarring
• Autoimmune disease
– ER stress results in:
• N F K B - m e d i a te d i m m u n e a c t i va t i o n
• A b e r ra nt a nt i ge n p re s e nta t i o n i n c e l l s u n d e rgo i n g
a u to p h a g y o r a p o p to s i s
• G e n e ra t i o n o f a u to a n t i ge n s
• S h a p i n g o f C D 4 T h e l p e r c e l l s u b s e t s
Nogee NEJM 2001, Lawson PNAS 2011, Todd Nat Rev Imm 2008, Hasnain Immunol Cell Biol 2012

21. Patient lungs demonstrate increase in
ER stress protein BiP

22. Patient BLCLs demonstrate
elevated levels of ER stress
CO – control
HC – healthy carrier
PA – patient
TG – thapsigargin

23. Expression of mutant COPA
causes an increase in ER stress

24. How might ER stress be linked to the
clinical phenotype in patients?

25. ER stress results in generation of Th17
priming cytokines in APCs
• KDEL-retained antigen in B lymphocytes induces a proinflammatory
response: a possible role for endoplasmic reticulum stress in adaptive T
cell immunity. J Immunol 2008
• HLA-B27 misfolding and the unfolded protein response augment
interleukin-23 production and are associated with Th17 activation in
transgenic rats. Arthritis Rheum 2009
• Endoplasmic reticulum stress-induced transcription factor, CHOP, is crucial
for dendritic cell IL-23 expression. Proc Natl Acad Sci 2010
• Proinflammatory Th17 cells are expanded and induced by dendritic cells in
spondylarthritis-prone HLA-B27-transgenic rats. Arthritis Rheum 2012

26. BLCLs with mutant COPA express Th17
priming cytokines
Th17 primingTh2 primingTh1 priming
CO – control
HC – healthy carrier
PA – patient
TG – thapsigargin

27. CD4 T cells from patients are polarized to
Th17 phenotype
B
A

28. Summar y
• WD40 COPA mutations cause autoimmune-
associated lung & joint disease
• 1st description of a vesicular trafficking
defect as cause of autoimmunity
• Identification of a novel molecular link
between ER Stress and autoimmunity
• Identification of a putative immunological
mechanisms by which:
mutant COPA ⟶ ER Stress ⟶ Th17 cells

29. Acknowledgements
SHUM LAB
• B i r t h e J e s s e n
• C h r i s L a w
• M a x J a n
• W i n t Lw i n
• O s c a r E s t ra d a
T h e p a t i e n t s & t h e i r fa m i l i e s
F u n d i n g a g e n c i e s :
B AY L O R C O L L E G E O F M E D I C I N E
• L e v i Wa t k i n s & J o rd a n O ra n g e
• W. W i s z n i e w s k i & J i m L u p s k i
U C S F
• N o a h Z a i t l e n
• P u i Kw o k & Pa u l Ta n g
• K i r k J o n e s
• F e ro z Pa p a & M a i ke T h a m s e n
• M i ke Ro s e n b l u m
• M i ke Wa te r f i e l d , M i c k i e C h e n g
& M a r k A n d e rs o n
• R a n d y S c h e k m a n ( U C B e r ke l e y )
To r o n t o S i c k K i d s
• S h a ro n D e l l
R 0 1 H L 1 2 2
5 3 3
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