Protein kinases : Role in cell signaling & implication in human

pathologies

Jayanti Tokas1, Rubina Begum1, Shalini Jain2 and Hariom Yadav2

1Department of Biotechnology, JMIT, Radaur

2 NIDDK, National Institute of Health, Bethesda,MD20892, USA

Email: yadavhariom@gmail.com

Protein Kinase

30% of all proteins may be modified

518 protein kinase genes=human kinome space

20% of all eukaryotic genes(human genome project)

218 genes=human diseases

Approx 30=tumor suppressor

Approx 100 dominant oncogenes

Kinases Protein phosphorylation cell signalingKinases Protein phosphorylation cell signaling

Reversible protein phosphorylation as a biological regulatory mechanism

Edmond H. Fischer and Edwin G. Krebs (1992 Nobel Prize for Physiology and Medicine).

Post-translational modification in the cell

• Cell growth/proliferation• Differentiation• Viability/survival• Homeostasis• Effector function (e.g. cytotoxicity, cytokine production)• Cell death

‘signal’

Signal Transduction and Kinase Pathways

Nucleus MAP kinase,• Transcription factors– Bind consensus sequence on

promoter– May form complexes– May itself be transcribed following cellular activation

Adaptor proteins

Effector enzymes

Classification

On the basis of amino acid :

Tyrosine kinases,

Serine threonine (PKC, Plk,Rho Kinases)

Receptor (EGFR,FGFR,PDGFR)

non receptor (JAK,src,Abl,MAPK)

Tyrosine kinase

structure

function:

Related pathologies

Serine threonine kinases Related pathology

Check points

Check points

Structure

Bioblar structure

N and c

N-beta sheets

C-alpha helix

ATP bind-cleft at intetrsection

How they function:

Mechanisms of Activation of Normal TKs.

survivalDifferentiation Motility Proliferation

May oligomerise

ControlAutoinhihibitory transmembrane interactions cytoplasmic juxtamembrane region further inhibits the enzyme by interacting with the kinase domain Autophosphorylation---. reorient critical amino acid residues increasing catalytic activityinhibitor proteins and lipidsIF CONTROL LOST

Loss of function

Gain of function

Mechanisms of TK Dysregulation

oPDGF EGFVEGFFGFKL

oPDGFREGFRHER2c-KITFGFR3

Overexpression of receptor or ligand

EGFRSuperfamily with 4 receptors

C-ERBB

C-ERBB2

C-ERBB3

C-ERBB4

Cell proliferationInhibition of apoptosisAngiogenesisCell motilitymetastasis

Carcinogenesis:colorectal cancer, lung cancer(enhanced responsiveness),glioblastoma

multiforme(constitutive active)

Over expressed & mutated

Deletions(exon 2-7:alternative splicing)

or point mutations(Ile654Val)

Dysregulation

Cell proliferation inh of apoptosis angiogenesis metastasis

Check points

FLT3

C-KIT

PDGFR

EGFRHER2

Mutation in receptor tyrosine kinase causing constitutive expression

PDGFR

Tyrosine kinase

fibroblasts,smooth muscles of lung and airways

Mesenchymal cell migration and proliferation

Angiogenesis and blood vessel maintainance

Dysfunction:

Abnormal vasulature irregular diameter leakiness

• Glioblastoma

• Atherosclerosis

• Pathological conditions:del(4q12) ; t(4;22)

• Adenocarcinoma

• Breast

• Colon

• Prostate

• Stomach

Cell growth

Differentiation

Chemotaxis

Angiogenesis

Cell survival

SKELETAL SYSTEM

Dysfunction

60 mutations

FGFR2 craniosynostosis syndrom(premature ossification of skull)

Pfeiffer syndrome(additional fingers

FGFR3 achondroplasia(dwarfism)

Gly380Arg Gly375Cys

Carcinogenesis:prostate, cervical ,bladder, colorectal cancer

FGFR(1-4)

Check points

Fusion of TK to partner protein

ABLPDGFRFGFR1

FGFR3JAK2

Bcr-Abl

C-Abl

Non receptor tyrosine kinase

Role:

Regulation of cell cycle,cellular response to genotoxic stress

Apoptosis neuronal development

Regulation :actin binding PI3 binding

C-Bcr localised in cytoplasm during mitosis(role in cell cycle regulation)

Bcr-Abl

t(9:22)

Related to CML(chronic myeloid leukemia)

prevent apoptosis even in the absence of growth factors

Mitogenic signaling

Altered adhesion to matrix

TARGET-imatinim mesylate

mechanism

Check points

A serine threonine kinase:PKC

Response to

•Growth factors

•Hormones

•Drugs

11 related kinases

Unregulated in GIST

Diagnostic marker therapeutic target

Therapeutic targetsATP binding domain inhibitors Erbstatin

Targeting Receptor

Monoclonal antibodies

• Herceptin, licensed for Her 2 receptor-positive

• Breast cancer

Small molecular inhibitors

Various protein tyrosine kinase inhibitors

TYRosine PHOSphorylation INhibitors

tyrophosphins

Competitive with substrate(eg.Itaconic acid)

Competitive with ATP(Quinolines)(main thrust) ATP binding fold more

specific

1. How many other kinase targets opened for exploration?

2. Majority of kinases remain largely uncharacterized.

A LOOK AHEAD

Current challenges and future directions

THANK YOU