Presentation is loading. Please wait.

Presentation is loading. Please wait.

[Vierstra, 2003 TIPS]. Ubiquitin/26S proteasome pathway Ub + ATP E1 E3 E2 Target Ub Target 26S proteasome UbiquitinationProteolysis + ATP Simplified.

Similar presentations


Presentation on theme: "[Vierstra, 2003 TIPS]. Ubiquitin/26S proteasome pathway Ub + ATP E1 E3 E2 Target Ub Target 26S proteasome UbiquitinationProteolysis + ATP Simplified."— Presentation transcript:

1 [Vierstra, 2003 TIPS]

2

3 Ubiquitin/26S proteasome pathway Ub + ATP E1 E3 E2 Target Ub Target 26S proteasome UbiquitinationProteolysis + ATP Simplified

4 WTrpn10-1 Loss of 26S proteasome function Smalle et al., 2003 Loss of proteasome function in the rpn10-1 mutant, leads to growth inhibition and the accumulation of polyubiquitinated target proteins.

5 Diversity in Ubiquitination Machinery is largely provided by the many E3s Single E1 Few E2’s Many E3’s

6 E3 structure/function E2 bindingTarget binding Ub E2 Target protein E2 bindingTarget binding Target protein Ub E2 E3 (Ubiquitin ligase)

7 E3 structure/function Ub E2 bindingTarget binding Target protein E3 Ub Target protein Ub 26S proteasome Ub

8 Number of E3s per genome Saccharomyces cereviseae Caenorhabditis elegans Drosophila melanogaster Homo sapiens Arabidopsis thaliana

9 1)Fast response to a change in signal intensity: direct control of protein activities in contrast to transcriptional regulation that involves transcription, transcript processing and translation steps before protein abundance is increased. 2) Proteolysis control can rapidly increase as well as decrease a proteins activity (only an increase is possible with transcriptional regulation). 3) Accurate reflection of signal intensity in response output : secundary modifications such as phosporylation/dephosphorylation can also directly change a proteins activity. However since such controls tend to be leaky, i.e. are the result of modification/demodification equilibria, their outcome depends on the initial abundance of the target protein. Advantages of proteolysis control in signal transduction

10 Why more E3s in plants? From Kepinski and Leyser, 2003 * More E3s means more proteolysis control of signaling. * Energetically wasteful? * Animals can side-step adverse environmental conditions. The sessile plant must endure. Plants need to be more sensitive to environmental changes. * Proteolysis control of signaling allows for quick responses to changes in signal intensities (changes in environmental conditions). * Proteolysis control also allows for an accurate response- strength to signal-intensity ratio. * Allows for a constant state of readiness. * Plants are less energy-limited.

11 Signal transduction leads to destabilization of a repressor of the response or stabilization of a response activator. This is accomplished via secundary modification (phosphorylation or dephosphorylation) of the target protein that leads to or prevents its detection by a Ubiquitin ligase (E3). Alternatively, signaling directly controls E3 affinity for the target protein. Controlling the activity of a protein via its degradation rate allows for faster and more accurate responses to changing concentrations/intensities of the signal (changing environment). Proteolysis control of signaling

12 The Ub/26SP pathway and signaling Describe two mechanisms that can be used to transform a signal into a response via the regulated degradation of a repressor of this response. Show how increased signal intensity leads to an increased response output.

13 The Ub/26SP pathway and signaling Describe two mechanisms that can be used to transform a signal into a response via the regulated degradation of an activator of this response. Show how increased signal intensity leads to an increased response output.

14 Response repressor * Signal (variable) Response (variable) DNARNAResponse repressor Constitutive expression R e s p n s e r o o s s e e r r p E3 Control of gene expression via conditional proteolysis EXAMPLE 1:

15 Response activator * Signal (variable) Response (variable) DNARNAResponse activator Constitutive expression R e s p n s e a c t i v r o o E3 Control of gene expression via conditional proteolysis EXAMPLE 2:

16 ABA response (Vierstra, 2009)

17 Response activator Signal (variable) Response (variable) DNARNA R e s p n s e a c t i v r o o Constitutive expression E3 Control of gene expression via conditional proteolysis EXAMPLE 3:

18 HY5 Light (variable) Light responses (variable) DNARNA R e s p n s e a c t i v r o o Constitutive expression COP1 Control of gene expression via conditional proteolysis EXAMPLE 3: Photomorphogenesis

19 COP1 acts as an E3 to target HY5 for degradation RING CoilWD-40 repeats E2 Ub E1 Ub E2* bZIP Degradation via 26S Proteasome COP1 HY5 Ub (Osterlund et al.,2000) Ub COP1 HY5 Degradation by the 26S proteasome

20 Photomorphogenesis Light intensity (Osterlund et al., 2000) HY5 LIGHT COP1 LIGHT RESPONSES

21 Response repressor Response (variable) DNARNA Constitutive expression Signal (variable) E3 R e s p n s e r o o s s e e r r p Control of gene expression via conditional proteolysis EXAMPLE 4:

22 AUX/IAA factors Auxin Response (variable) DNARNA Constitutive expression Auxin (variable) TIR1 R e s p n s e r o o s s e e r r p Control of gene expression via conditional proteolysis EXAMPLE 4: Auxin response pathway

23 Auxin response (Vierstra, 2009)

24 Jasmonate response (Vierstra, 2009)

25 1)How does a target protein become polyubiquitinated through the sequential action of E1, E2 and E3 enzymes? 2)26S Proteasome: structure/function. How does the proteasome detect and then degrade target proteins? 3)Where in the cell does the Ubiquitin/26S Proteasome pathway act? 4)ATP requiring steps in the pathway? Energy is needed to establish specific proteolysis (as opposite to non-specific). 5)Predict the effects of loss of function of different components of the pathway (proteasome --- pleiotropic; E3 --- highly specific phenotype). 6)Why proteolysis control of signal transduction (what are the advantages)? 7)Possible mechanisms of conditional protein degradation to control signal/response ratios (see examples 1-4). Summary: important to remember

26 2011

27 2009

28 2008


Download ppt "[Vierstra, 2003 TIPS]. Ubiquitin/26S proteasome pathway Ub + ATP E1 E3 E2 Target Ub Target 26S proteasome UbiquitinationProteolysis + ATP Simplified."

Similar presentations


Ads by Google