Cell death vs Cell life

Characteristic morphologic features of apoptosis Extr signal Intr signal nucleus DNA fragmentation (formation of nucleosomal fragments) Cytoplasm and nucleus condensation. Cell shrinks mitochondria Membrane blebbing and formation of apoptotic bodies Apoptotic bodies are removed by phagocytes

Characteristic morphologic features of necrosis Extr signal nucleus mitochondria DNA clumping without significant fragmentation Cytoplasm and organelle swelling, organelle destruction Cell burst Cytoplasm components spill out into tissue

DNA damage p53 p53 activation mitochondria Cytochrome C releasing from mitochondria into cytoplasm p53BAX gene transcription p53Bcl-2 gene inhibition BAXBcl-2 BAX Bcl-2 Initiation: intrinsic pathway (mitochondria- dependent pathway)

Bax and Bak produce pores for the cytochrome c efflux

p53 and the Bcl-2-family p53 activates transcription of pro-apoptotic proteins Bax, Bak, PUMA and Noxa p53 inhibits transcription of anti-apoptotic proteins Bcl- 2, BCL-2XL p53 might displace Bax/Bak from inhibitory complexes with anti- apoptotic Bcl-2-like proteins Galluzzi et al., 2008

Initiation: intrinsic pathway (mitochondria-dependent pathway) Cytochrome C released from mitochondria into cytoplasm Procaspase 9 Active caspase9 Caspase 9 activation Caspase 3/6/7 activation apoptosis

Initiation: extrinsic pathway (death receptor-mediated pathway) TNF – tumor necrosis factor (ligand) TNFR – tumor necrosis factor receptor DD – death domain TRADD - TNF receptor- associated DD FADD - Fas- associated DD TNF/TNFR/TRADD/FA DD/Procaspase 8 complex is known as DISC ( death-inducing signaling complex) cell Death domain (DD) TNF TNFR TRADD FADD Procaspase 8 Activation of Caspase 8 Activation of Caspase 3 apopt osis

Signal transduction, cell growth and apoptosis Growth factors: Survival factors – inhibition of apoptosis Mitogens – cell division Growth factors – increase in sizes Death factors

Survival factors Cell compete for survival factors Adequate amount of survival factors prevents apoptosis via the PI3K/Akt- controlled pathway via activation of one factors and inibition of others NF-kB, Bcl-2 and TOR/MCL1 ( myeloid leukemia cell differentiation protein ) are major effectors that prevent apoptosis Bax/Bad/caspases are direct Akt targets that are inhibited Hein et al., 2014

AKT-dependent survival pathway AKT phosphorylates and inhibits Bax and Bad AKT activates mTOR, which in turn phosphorylates and activates antiapoptotic protein MCL-1 (induced myeloid leukemia cell differentiation protein). AKT also activates NF- κ B thus resulting in transcription of pro-survival gene Bcl-XL (B- cell lymphoma-extra large). NF- κ B phosphorylates the X- linked inhibitor of apoptosis protein (XIAP), then binds to and inhibits caspases. AKT phosphorylates FOXO3 protein (Forkhead box O3) that inhibits Bim (Bcl-2 interacting mediator of cell death) and Noxa proapoptotic proteins Kalimuthu and Se-Kwon, 2013

Mitogens Mitogens promote G1/S transition Mitogens activate TKRs TKRs activate the MAPK and PI3K/Akt//NF-kB cascades MAPK and NF-kB activate the Cyclin D expression – the Cdk4/6 Cyclin D complex etc.

Cell growth inhibitors Cell growth inhibiors can be physiological and pathological The best studied physiological growth inhibitor is myostatin

Death ligands Ligands of the TNF family engage apoptosis in a p53-independent manner Binding of these ligands to their cognate receptors induces receptor aggregation and the formation of a macromolecular complex, coined DISC (death-inducing signalling complex), which lead to apoptosis British Journal of Pharmacology Volume 169, Issue 8, pages , 26 JUL 2013 DOI: /bph Volume 169, Issue 8,