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Defining degradation pathways of RGS2 using high-throughput siRNA screening
1. Defining degradation pathways of
RGS2 using high-throughput siRNA
screening
Benita Sjögren, Ph.D.
Department of Pharmacology & Toxicology
2. Regulator of G protein signaling 2 (RGS2) as a drug target
GTP
α-GDP γ
β
GDP
α-GTP
γ
β
Pi
RGS
RGS protein active
α-GDP γ
β
GDP
α-GTP
γ
β
Pi
RGS SIGNAL
RGS protein enhanced
SIGNAL
GTP
RGS2 KO mice are hypertensive, show
prolonged response to vasoconstrictors (e.g.
Angiotensin II). Heximer et al. J Clin Invest. 2003 and
have worsened heart failure in TAC models.
Takimoto et al , J Clin Invest. 2009
Enhancing RGS2 function could be a
novel avenue in cardiovascular
therapeutics
But how to achieve it?
Blocking the enzymes
involved in RGS2 protein
degradation should
increase RGS2 protein
function
RGS2 is rapidly degraded through the ubiquitin proteasomal pathway
>600
3. siRNA screening approach
Gene involved in RGS2
protein degradation
RGS2 protein
chemiluminescence
48h at 37⁰C
siGENOME SMART POOL siRNA (Dharmacon)
“Druggable genome” Subset ~3,200 genes
Lipofectamine RNAiMAX
+ SMART POOL (triplicate)
384-well plateAdd cells
384-well plate Celltiter Fluor viability assay
PathHunterTM ProLabel assay
Controls:
Non-targeting siRNA
RGS2
Viability PLK-1
siTOX
Kif-11
DAVID david.abcc.ncifcrf.gov
GeneGo portal. genego.com
PathHunter ProLabel assay, DiscoveRx
Stable HEK-293 cell line
Top hit genes involved in ubiquitin-proteasomal
degradation was F-box protein 44 (FBXO44) and
Cullin 4B (CUL4B)
4. RGS2 is degraded by a novel CUL4B/DDB1/FBXO44 E3 ligase
RGS2chemiluminescence
(%change)
R
G
S
2
F
B
X
O
4
4
C
U
L
4
A
C
U
L
4
B
-7 5
-5 0
-2 5
0
2 5
5 0
7 5
1 0 0
1 2 5
1 5 0
***
***
***
s iR N A
RGS2-HAproteinhalf-life(min)
N
T
F
B
X
O
4
4
C
U
L
4
A
C
U
L
4
B
0
1 0
2 0
3 0
4 0
5 0 ***
*
s iR N A
RGS2proteinlevelsRGS2proteinhalf-life
X
RGS2 protein levels
Funding: NIGMS (R01 GM110195), American Heart Association (15SDG21630002)
MSU
Richard Neubig
Center for Chemical Genomics
Martha Larsen
Steven Swaney
University of Iowa
Kevin Glenn