ubiquitin degradation with its substrate, or as a monomer in a ubiquitination-independent mode,...
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Ubiquitin degradation with its substrate, or as amonomer in a ubiquitination-independent mode,provides clues to proteasome regulation
Nitzan Shabek1, Yifat Herman-Bachinsky1, and Aaron Ciechanover2
Cancer and Vascular Biology Research Center, Rappaport Faculty of Medicine and Research Institute, Technion-Israel Institute of Technology,Haifa 31096, Israel
Contributed by Aaron Ciechanover, May 27, 2009 (sent for review April 21, 2009)
www.pnas.org PNAS July 21, 2009 vol. 106 no. 29 11907–11912
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Vias proteolíticas
LisossomalDependente de cálcio
Ubiquitina-proteassomaResidual
Mas, quem degrada os componentes das vias???
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Vias proteolíticas
Lisossomal ?Dependente de cálcio ?
Ubiquitina-proteassomaResidual ?
Mas, Quem degrada os componentes das vias???
LisossomalEste trabalho....
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Ubiquitina
Regulação dos níveis em diferentes condições é desconhecidaEstudos anteriores: Degradação não lisossomal e dependente de ATPMeia-vida em torno de 10 hs.Mal funcionamento das DUBS aumentam a degradação de Ub juntamente com seu substrato-alvo.
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Ubiquitina Como ocorre a degradação de Ub pelo proteassoma (Ub livre ou conjugada com seus substratos-alvo?)
Investigar mecanismos de ligação entre substratos e componentes do proteassoma
Impede que seja usada como Ub marcadora e que seja clivada no c-terminal por Proteases específicas para Ub
Nitzan Shabek, Kazuhiro Iwai, Aaron Ciechanover Ubiquitin is degraded by the ubiquitin system as a monomerand as part of its conjugated target Biochemical and Biophysical Research Communications 363 (2007) 425–431
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Ubiquitina e proteassoma
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ATP- and proteasome-dependent degradation of WT (UbGG) and inert (UbVV)
Ubs. (i and ii) 125I- UbGG was subjected to in vitro degradation in reticulocyte
fraction II (FrII) in the presence or absence of ATP (i) and in the presence or
absence of the proteasome inhibitors MG132 (MG) or lactacystin (LC)(ii) (iii)
Degradation of 125I-UbGG was compared with that of 125I-UbVV. Bars
in ii and iii represent net ATP-dependent values.
Indução de formação de reticulócitos com fenilhidrazina
Dep. ATP
Dep. proteassoma
Não conjuga
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(B) Ubiquitination and degradation of 125I- UbGG in the presence and absence of added
MyoD. (i) 125I- UbGG was subjected to in vitro degradation t with or without MyoD (5 g).
(ii) Purified MyoD was subjected to degradation in vitro . (iii) 125I-UbGG and 125I-UbVV
were subjected to in vitro ubiquitination in the presence of HeLa cell extract or
reticulocyte FrII, ATP, and purified MyoD (5 g) as indicated.
Estimula
Ub é degradada como parte de seu substrato conjugado
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(C) ATP-dependent degradation (i) and ubiquitination (ii) of 125I-UbGG in the presence of
FrII. Purified MyoD and unlabeled iodine-modified BSA and RNase A were added as
indicated (5 g each). Degradation of labeled Ub was monitored by using release of TCA-
soluble radioactivity, and degradation of MyoD was monitored after SDS/PAGE and
Western blot analysis . Conjugation of labeled Ub was carried out as described in
Materials and Methods. All degradation values of Ub represent the average of 5
independent experiments (SD is shown). Ub conj. denotes Ub conjugates. Ub é degradada como parte de seu substrato conjugado
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Ub é degradada por UPS em um mecanismo (“piggyback”)
que envove seu substrato conjugado (ambos são
degradados conjuntamente)
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Fig. 2. Ubiquitination-independent degradation of extended Ubs
by the 26S proteasome
(A) cDNAs coding for the indicated UbVV variants was expressed
in HEK-293 cells, and the stability of the proteins was monitored after
the
addition of CHX. Proteins were visualized by using anti-Ub (i) or anti-
RGSHis
(ii–vii).
> 20 resíduos
N-terminal bloqueado
Sem lisinas (“lisineless”)
Não podem ser ubiquitinados
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(B) 35S-labeled UbVV variants were translated in S30 bacterial extract
(except for 35S-UbVVHisHA shown in viii that was translated in wheat
germ
extract) and subjected to in vitro ATP-dependent degradation in FrII
without
Ub. MG132 was added as indicated. The asterisk in viii marks
monoubiquitinated
UbVVHisHA that was generated during translation.
Sem Ub
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(C) His-tagged bacterially expressed and purified UbVVHisHA (i) and
UbVVHis (ii) were subjected to in vitro ATP-dependent degradation in
the presence of FrII (lanes 1–3) or purified 26S proteasome (lanes 4–
6). MG132 and Ub were added as indicated.Reaction mixtures were
incubated for 2 h. Proteins were detected by using anti-RGSHis
(Upper) or anti-Ub (Lower; membranes were reblotted).Ubs com extensões suficientemente longas podem ser degradadas sem ubiquitinação adicional
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(D) HEK-293 cells were transfected with cDNAs (in pCS2) coding for
UBB1/K29,48R, UBB1YK29,48R, andUBB1HAK29,48R, and their
stability was monitored after the addition of CHX.
UBB: gene com extensão de 19 resíduos, implicado na patogênese do mal de Alzheimer e outras doenças neurodegenerativas
Lys29 e Lys48 → Arg +Tyr +HAr
> 20 resíduos
Não ubiquitináveis
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(E) HEK-293 cells were transfected with cDNAs coding for UBB1HA,
UBB1HAK29,48R, and empty vector (EV). HA-tagged proteins were
immunoprecipitated as described in Materials and Methods, and the
association
with the proteasome was detected with the indicated antibodies. In all
experiments, proteins were resolved via SDS/PAGE.
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O proteassoma 26S pode ligar e degradar Ub
monomérica independentemente de
ubiquitinação
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Fig. 3. Inhibition of degradation of UPS substrates depends on ubiquitination of short, C-terminally extended nondegradable Ub
variants.
(A) (i) HEK-293 cells were cotransfected with cDNAs coding for the indicated UbVV
variants and UPS substrates (MyoD, Mdm2, or c-Myc), and the stability of the substrates
was monitored after the addition of CHX for the indicated times. (ii) Quantitative
representation of MyoD degradation as shown in i. (iii) Effect of the different UbVV
variants on the degradation of endogenous p21. The experiment was carried out in a
similar manner as described in i.
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(B) HEK-293 cells were transfected with cDNAs coding for
UbVVHis or UbVVHisHA, or their LL species. The stability of
endogenous p21 (i) or cotransfected c-MycHA (ii) was monitored
as described in A.Sem efeito inibitório
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(C) (i) cDNAs (in pcDNA3) coding for UBB1 or UBB1/K29,48R were cotransfected along with a
cDNA coding for c-MycHA, and the stabilities of endogenous p21 and the expressed Myc
were monitored as described in A. (ii) HEK-293 cells were transfected with cDNAs coding for
UBB1 and UBB1/K29,48R. Thirty hours after transfection, the total cell proteins were
resolved via SDS/PAGE, and Ub conjugates were visualized after Western blot analysis using
an anti-Ub conjugates antibody. Gels described in Ai and Cii were 10%. MG132 was added as
indicated
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Ubs de cadeias curtas inibem a degradação de substratos de UPS
pela sua habilidade de serem ubiquitinadas
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Fig. 4. Proteasome inhibition by extended Ub variants affects
only ubiquitination-dependent substrates.
(A)UbVVHis and LLUbVVHis interact with the 26S proteasome. Bacterially
expressed and purified UbVVHis (i) and LLUbVVHis (ii) were incubated in the
presence of HeLa cell extract. 26S proteasomes were precipitated by using anti-
6 (20S subunit) as described in Materials and Methods, and the Ub derivatives
and proteasome subunits were detected after SDS/PAGE and immunoblotting.
The input represents 10% of the lysate used for immunoprecipitation (IP)
Precipitam com o proteassoma
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(B) HEK-293 cells were cotransfected with cDNAs coding for
UbVVHis and Flag-ODC as indicated. The level of ODC was
monitored after the addition of CHX and MG132 at the indicated
times. ODC= Ornitina descarboxilase, degradada pelo proteassoma sem ubiquitinação Não inibiu a
degradação
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(C)HEK-293 cells were cotransfected with cDNAs coding for Flag-AZ and UbVVHis or LLUbVVHis as indicated, and the stability of AZ was monitored after the addition
ofCHXfor the indicated times.
AZ = antizima, regulador da ODC que a marca para degradação . AZ é degradada pelo proteassoma por ubiquitinação
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(D) Stabilities of transfectedFlag-ODCandFlag-AZ were monitored
in cells expressing UBB1 or UBB1/K29,48R (from pcDNA3) as
described in B and C.
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O efeito inibitório de derivados com extensões curtas de Ub afeta substratos dependentes de
ubiquitinação
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ConclusõesUb é degradada por UPS em um mecanismo
(“piggyback”) que envove seu substrato conjugado (ambos são degradados conjuntamente)
O proteassoma 26S pode ligar e degradar Ub monomérica independentemente de ubiquitinação
Ubs de cadeias curtas inibem a degradação de substratos de UPS pela sua habilidade de serem
ubiquitinadas
O efeito inibitório de derivados com extensões curtas de Ub afeta substratos dependentes de
ubiquitinação
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Fig. S1. UbVV variants have no effect on
DUB activity and the 20S catalytic
activity. (A) 35S-labeled UPS substrates
were subjected to ATP-dependent
ubiquitination in a cell-free system.
Reaction mixtures were incubated for 1 h
at 37 °C (in a volume of 10 L) in the
presence of E1 and E2 (UbcH5c for
Ring1B and XIAP-1, and Ubc7 for MyoD),
and then for an additional hour in the
presence of HeLa cell extract (50 g in a
total volume of 15 L; as source for DUBs
for
all substrates and MyoD’s E3). Ubal or 5 g
of purified UbVV variants was added as
indicated. Proteins were resolved by
SDS/PAGE (10%) and visualized by using
PhosphoImager
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(B) 26S proteasomes were isolated via immunoprecipitation from
HeLa cell extract, and the DUB-associated activity was monitored by
measuring
the cleavage of Ub-AMC after preincubation with UbVVHis,
LLUbVVHis, or Ubal as described in Materials and Methods, Fig. 4A,
and SI Text.
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(C) 20S proteasomal activity was monitored by using purified 26S proteasome and measuring the release ofAMCfromLLVY-AMCin the presence of ATP and increasing concentrations of
MG132, purified UbVVHis, or WT Ub as indicated. Activity was measured as described in SI Text.