Download Insulin Signaling

Insulin Signaling: A Molecular View
Shuchismita Dutta, Ph.D.
Developed as part of the RCSB Collaborative Curriculum Development Program 2016
Learning Objectives
• Energy in Biology
• Insulin Signaling
• Insulin Resistance and Type 2 Diabetes
Developed as part of the RCSB Collaborative Curriculum Development Program 2016
Learning Objectives
• Energy in Biology
• Insulin Signaling
• Insulin Resistance and Type 2 Diabetes
Developed as part of the RCSB Collaborative Curriculum Development Program 2016
Energy in Biology
• ATP: Energy currency of cells
• Main sources of ATP
Glycogen
Amino acids;
Glycerol etc.
----Adenine-----Adenosine--------------Adenosine monophosphate(AMP)
----Adenosine diphosphate(ADP)-----------Adenosine triphosphate(ATP)---------------
Substrate  Product
Metabolic Process
Glucose  Pyruvate
Glycolysis
Pyruvate  Acetyl CoA
Pyruvate Dehydrogenase
Acetyl CoA  CO2
Kreb’s Cycle
Free fatty acids  Acetyl CoA
Beta oxidation
Fats
Developed as part of the RCSB Collaborative Curriculum Development Program 2016
Glucose Homeostasis
• Pancreas produces
– Insulin
• Produced by b cells
• Promotes uptake of
glucose from plasma
– Glucagon
• Produced by a cells
• Promotes processes to
release glucose into
plasma
Developed as part of the RCSB Collaborative Curriculum Development Program 2016
Balancing Insulin and Glucagon
Incretins
GLP-1; GIP
(Gut cells)
Insulin production
– High blood glucose
– Glucagon
– Incretin hormones
• Glucose-dependent
insulinotropic peptide
(GIP)
• Glucagon-like-peptide 1
(GLP-1)
Glucagon production
Insulin
(b cells)
Glucagon
(a cells)
– Low blood glucose
– Insulin
Developed as part of the RCSB Collaborative Curriculum Development Program 2016
Somatostatin
(d cells)
Glucose Transporters
14 Types known; GLUT 1-4 characterized
•
•
GLUT1
– Main transporter in red blood cells and
blood-tissue barriers
– Ubiquitous; medium affinity
– For basal-level glucose uptake
•
Glucose Co-transporters
– Sodium Glucose co-transporters (SGLTs)
GLUT2
– Allows uptake and efflux of glucose in
response to fed or fasted state
– Mediates transport in liver, intestinal,
kidney and pancreatic cells
– Low affinity
•
GLUT3
– Primary function in neurons, and
circulating white blood cells
– High affinity
•
GLUT4
– Responsive to insulin
– In adipocytes and muscle (skeletal and
cardiac) cells
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4104978/figure/F6/
Developed as part of the RCSB Collaborative Curriculum Development Program 2016
http://www.nature.com/nature/journal/v526/n7573/full/nature14655.html
Transporter GLUT3 in Action
Movie at
http://www.nature.com/natu
re/journal/v526/n7573/fig_t
ab/nature14655_SV3.html
Developed as part of the RCSB Collaborative Curriculum Development Program 2016
Learning Objectives
• Energy in Biology
• Insulin Signaling
• Insulin Resistance and Type 2 Diabetes
Developed as part of the RCSB Collaborative Curriculum Development Program 2016
Insulin Signaling
Insulin Receptor
Insulin
Insulin-Insulin Receptor Complex
Extra-cellular
Transmembrane
Cytoplasmic
http://pdb101.rcsb.org/motm/182
Developed as part of the RCSB Collaborative Curriculum Development Program 2016
Insulin Receptor
Insulin Receptor
L2
FnIII-1
L1
aCT
FnIII-2
CR
Extra-cellular
FnIII-3
Transmembrane
Cytoplasmic
http://pdb101.rcsb.org/motm/182
http://www.ncbi.nlm.nih.gov/pmc/articl
es/PMC3793637/
Developed as part of the RCSB Collaborative Curriculum Development Program 2016
Ecto IR, PDB ID 3loh
Insulin Binding to Receptor
Insulin-Insulin Receptor Complex
Ins:mIR complex,
PDB ID 3w14
a-CT of second IR protein interacts with insulin and first IR
molecule
http://pdb101.rcsb.org/motm/182
Developed as part of the RCSB Collaborative Curriculum Development Program 2016
Insulin Signal Transduction
• IR Tyrosine Kinase
domain:
– Inactive state (PDB ID 1irk)
a mobile loop blocks entry
of substrate
– Active state (PDB ID 1ir3) several tyrosines on this
loop are phosphorylated,
 loop swings out of
active site, allowing ATP
and other signaling
proteins to bind.
– Active site uses ATP to
phosphorylate its targets.
Tyrosine Kinase domain of IR showing inactive
(PDB ID 1IRK) and active (PDB IDs 1IR3) forms
Insulin Signaling
1. Insulin
binds
6. Protein Synthesis
7. Cell Survival
8. Proliferation
2. Tyrosine
Kinase
activation
4. Translocate
GLUT4 transporters
5. Glucose
uptake
Metabolism
3. Signaling
molecules: IRS, PI3K,
PDK1, AKT, AS160
etc.
Glycolysis
ATP + Pyruvate
Lipogenesis
Lipids
Developed as part of the RCSB Collaborative Curriculum Development Program 2016
Storage
Glycogenesis
glycogen
Insulin Signal Transduction
PIP2
IRS
P
PIP3
PI3K
P
PKC
Translocate to
Glucose
uptake
PDK1
Glycogen Synthesis
P
GSK3
Gluconeogenesis
FOXO1
Protein Synthesis
mTORC1
AKT2
P
AS160
P
mTORC2
Developed as part of the RCSB Collaborative Curriculum Development Program 2016
GLUT4
vesicle
Insulin Signal Transduction
PIP2
IRS
P
PIP3
PI3K
P
PKC
PDK1
PTP1B
Glycogen Synthesis
PTEN
P
GSK3
Glyconeogenesis
FOXO1
Protein Synthesis
mTORC1
AKT2
Translocate to
Glucose
uptake
P
AS160
P
mTORC2
Developed as part of the RCSB Collaborative Curriculum Development Program 2016
GLUT4
vesicle
Understanding AKT
P
AKT2
P
• N-terminal PH domain
localizes AKT to plasma
membrane (levels of
PI(3,4,5)P3 or PI(3,4)P2)
• Catalytic domain
activated by
phosphorylation of Thr
– T309 by PDK and S474
by mTORC1
AKT Kinase domain showing inactive (PDB ID
1MRV) and active (PDB IDs 1O6L) forms
Learning Objectives
• Energy in Biology
• Insulin Signaling
• Insulin Resistance and Type 2 Diabetes
Developed as part of the RCSB Collaborative Curriculum Development Program 2016
Insulin Resistance
• Insulin is present but signaling is
disrupted at the level of IRS, AKT, AS160,
etc.
• Body tries to compensate by making more
insulin
PIP2
IRS
P
PIP3
PI3K
P
PKC
Glucose
uptake
PDK1
Glycogen Synthesis
P
GSK3
Glyconeogenesis
FOXO1
Protein Synthesis
mTOR
AKT2
P
AS160
P
mTOR/
Developed as part of the RCSB Collaborative Curriculum Development Program 2016
GLUT4
vesicle
A Case of Insulin Resistance
• A family with severe insulin resistance and
diabetes due to a mutation in AKT2 Science. 2004 May 28; 304:1325-8.
• Molecular Exploration … (see hands-on
exercise attached)
What May Happen in R274H
Active Site
Residues
R274
Substrate peptide
PDB ID 1o6l, Yang et al., 2002
TPO 309
Mutation of Arg
274 to His would
disrupt the
H-bonds holding
the activation
loop in the active
state
Summary
• Energy in Biology
– ATP is energy currency
• Insulin Signaling
– Reception, Signal Transduction and Response
• Insulin Resistance and Type 2 Diabetes
– Mutations may disrupt proteins in Insulin signaling
Developed as part of the RCSB Collaborative Curriculum Development Program 2016