birds eye view

1. DIACYLGLYCEROL
SIGNALING PATHWAY
PREPARED BY YONAS TESHOME
DEPARTMENT OF MEDICAL PHYSIOLOGY
4/28/2016
6/21/2016
byYonasTeshome
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2. Outline
 Objectives
 Introduction
 Dawn stream effectors of DAG
 PKC induced cellular processes
 The DGK, RasGRP, PKD, Chimaerins, and Munc 13
 Summary
 Reference
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3. Objectives
At the end of this session you will be able to:
 Define diacylglycerol
 Describe the signaling pathways of diacyleglycerol
 List the down stream effectors of DAG and
 List some of the cellular processes takes place by DAG through PKC
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4. Introduction
 Diacylglycerol (DAG) is a lipid signal messenger which is an
essential second messenger in mammalian cells.
 Is glycerol derivative that have two hydroxyl groups esterified by
fatty acids.
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R and R' are saturated or unsaturated hydrocarbon chains

5. Cont...
 Key enzymes in most of the signaling processes that generate DAG are the
phosphatidylinositol 4,5-bisphosphate- specific phospholipase C isozymes.
 Hydrolysis of Phosphatidyl inositol 4,5 bisphosphate (PIP2) by PLC causes the
formation of DAG and inositol 1,4,5-trisphosphate (IP3).
 In compared to IP3, DAG is very nonpolar molecule therefore it remain in the
membrane while IP3 is released into cytosol.
 In addition, DAGs are produced from phosphatidylcholine (PC) by two
subsequent reactions involving two mammalian PC-specific phospholipase D
isozymes (PCPLDs) and phosphatidic acid phosphohydrolase.
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6. Cont…
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7. Cont…
 The most prominent downstream effector of diacylglycerol and the functionally
analogous phorbol esters belong to the protein kinase C family, but at least five
alternative types are known:
 Protein kinase D,
 RasGRPs,
 Chimaerins, and
 Munc13s.
 These can functions independently of protein kinase C isozymes, and regulates
processes as diverse as gene transcription, lipid signaling, cytoskeletal dynamics,
intracellular membrane trafficking, or neurotransmitter release.
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8. Signaling pathway through PKC
 Protein kinase C is a family of protein kinase enzymes that are involved in
controlling the function of other proteins through phosphorylation.
 They are divided into three subfamilies, based on their second messenger
requirements:
 Conventional (c)PKCs contain the isoforms α, βI, βII, and γ. These require
Ca2+, DAG, and a phospholipid such as phosphatidylserine for activation.
 Novel (n)PKCs include the δ, ε, η, and θ isoforms, and require DAG, but do
not require Ca2+ for activation.
 Atypical (a)PKCs includes ζ and λ isoforms.
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9. Cont…
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10. PKC signaling induced cellular processes
 PKC is involved in regulation of diverse cellular processes including
proliferation, differentiation, neural development, synaptic transmission, axonal
regeneration, smooth muscle contraction, gene expression, etc.
Example: Cell proliferation by PKC signaling
 Activation of PKC induces phosphorylation of transcription factor serum
response factor (SRF).
 SRF regulates immediate early genes (IEGs) such as Egr-1 (early growth
response gene 1) that control cell proliferation.
 Immediate early genes with proteins such as c-jun, c-fos, myc which are
transcription factors and activate target gene resulting in cell proliferation.
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11. Acute stress
Hypoxia
Ischemia
Chronic stress
Atherosclerosis
Restenosis
PKCβ
Egr-1
Cytokines, Chemokines
Procoagulant molecules
Adhesion molecules
Inflammation, Migration, Proliferation
Vascular dysfunction
Tissue injury
Example 2 PKCβ – Egr-1 in vascular stress response
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12. cont…
 PKCθ plays important roll in T cell activation by activating Nuclear factor kappa-
light-chain-enhancer of activated B cells (NF-kβ), activator protein 1(AP1),
Nuclear factor activating T cell (NFAT), T cell proliferation by IL2( inter leukin
2), Cell apoptosis by FasL.
 PKC is anchored to membrane by specific proteins often localized to specific
subcellular sites. This PKC anchoring proteins are named receptors for activated
C kinases (RACKs).
 Therefore cells often regulates PKC effect according to their need by RACKs.
Cell type.docx
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13. Other down stream effectors of DAG
 Protein kinase Ds The PKD family in mammals consists of PKD1,
PKD2, and PKD3.
 All PKDs contain two C1 domains, a negatively charged central
domain, a pleckstrin homology (PH) domain, and a serine/threonine
protein kinase catalytic domain. PKD1 contains an additional
amino-terminal apolar domain.
 The major PKD activation mechanism involves phosphorylation by
PKCα, PKCε, and PKCη at sites in the regulatory domain
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14. Cont….
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15. Cont…
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PKD regulate processes like signal transduction, membrane trafficking, and cell
survival, migration, differentiation, and proliferation.

16. Cont…
 Through their RasGEF domains, most RasGRPs(Ras guanyl
nucleotide-releasing protein) promote GDP/GTP exchange and
activation of Ras and related small GTPases, which leads to the
stimulation of the Raf-MEK-ERK cascade and to the regulation of
other signaling pathways.
 Through activation of the Raf-MEK-ERK pathway, RasGRPs have
been implicated in cell differentiation, cell proliferation, cell
transformation, T-cell receptor signaling, T cell differentiation, B-
cell receptor signaling, and neuronal differentiation.
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17. Cont…
 Chimaerins the first high affinity non-PKC DAG/PE receptors
discovered, By inactivating Rac, necessarily interfere with all
downstream effects of Rac (e.g. formation of lamellipodia and
membrane ruffles, and loss of stress fibers).
 Generally, chimaerins are implicated in diverse cellular processes
such as cell adhesion, cytoskeletal dynamics, lamellipodia/
filopodia formation, phagocytosis, and cell proliferation.
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18. Cont…
 Munc13s act by unfolding and activating the soluble N-ethyl
maleimide sensitive factor attachment protein receptor (SNARE)
protein Syntaxin and thereby promoting SNARE complex
formation and secretory vesicle priming.
 Munc13s rather than PKCs are the only functionally relevant DAG
sensitive presynaptic regulators of transmitter release. Similarly,
insulin secretion from pancreatic b cells is increased by Munc13
action in experiment.
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19. Regulation of DAG
 DAG kinases phosphorylate DAG to form phosphatidic acid.
 DAG kinases have a major role in intracellular signaling in which
they terminate the DAG signal generated by PLCs and form
phosphatidic acid, which itself is a signaling molecule.
 DAG kinases are thought to be active only in spatially restricted
compartments following physiological DAG generation.
 One such subcellular compartment is the cytoskeleton where DAG
kinases might regulate cytoskeletal dynamics by producing
phosphatidic acid, which would affect actin capping proteins and
actin polymerization. 6/21/2016by Yonas Teshome
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20.  In addition, DAGkinase dependent regulation of DAG and
phosphatidic acid levels affect GTPase activating proteins for Rho
family members and certain DAG kinases interact directly with
Rho GTPase.
 DAG kinases(α,β,γ) are also constitutively localized in or recruited
to nuclear compartments where they are thought to regulate a
strictly compartmentalized DAG signaling pathway that controls
cell proliferation.
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21. Summary
 DAG is an essential second messenger in mammalian cells.
 DAG is formed by hydrolysis of PIP2 by an enzyme called PLC.
 Intracellular targets of DAG are: Protein kinase C, Protein kinase D, RasGRPs,
Chimaerins, and Munc13s.
 As a second messenger DAG signals diverse cellular processes including
proliferation, differentiation, neural development, synaptic transmission, axonal
regeneration, smooth muscle contraction, gene expression, etc.
 DAG kinases have a major role in intracellular signaling in which they terminate
the DAG signal generated by PLCs with receptors for activated C kinases
(RACKs).
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22. References
 N. Brose, A. Betz and H. Wegmeyer, Divergent and convergent signaling by the
diacylglycerol second messenger pathway in mammals
 Yukiko K. Kaneko* and T. Ishikawa, Diacylglycerol Signaling Pathway in
Pancreatic β-Cells: An Essential Role of Diacylglycerol Kinase in the Regulation
of Insulin Secretion, Shizuoka 422–8526, Japan. Received January 20, 2015
 https://en.wikipedia.org/wiki/Protein_kinase_C
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23. THE END!
THANK YOU
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