Cell Biology

... from active transport to vesicles


Apoptosis: Modified: Caspases (cysteinyl aspartate-specific proteases) are enzymes that cleave specific proteins at aspartate residues, and which contain cysteine residues at their active sites. Many caspase isoforms are promoters of apoptosis. Caspases can be activated by the death receptor pathway and the mitochondrial pathway.

At least 14 caspase isoforms have now been identified, and the isoforms are broadly categorised into initiators, effectors and inflammatory caspases. Initiator caspases such as caspase-8 and 9 cleave and activate effector caspases such as caspase-3. Effector caspases cleave specific proteins that ultimately leads to cell death by apoptosis. Caspase activity leads to a proteolytic cascade in which one caspase can activate other caspases, thus amplifying the apoptotic signalling pathway.

Cleavage of proteins by caspases can either activate them (other caspases, ICAD), or they can deactivate them (PKB/Akt, Raf-1, PARP-1). In general, proteins that promote apoptosis are activated, and proteins that promote survival are inactivated.

Tables  Apoptosis vs Necrosis  Apoptosis 

• A • adhesion • C • cell membranescellular adhesion moleculescellular signal transductioncentrioleschemotaxischloroplastcilia & flagellacommunicationconcentration gradientscytokine receptorscytoplasmcytoskeleton • E • energy transducersendoplasmic reticulumendosomesexosome • F • flagella & cilia • G • Golgi apparatusGPCRs • H • hormones • I • ion channels • L • lysosome • M • meiosismicrotubulesmitosismitochondrion • N • Nitric Oxideneurotransmissionneuronal interconnectionsnuclear membranenuclear pore • P • pinocytosisproteasomeprotein degradationpumps • R • receptor proteinsreceptor-mediated endocytosis • S • second messengerssignaling gradientssignal transductionspindlestructure • T • transporttwo-component systems • U • ubiquitin • V • vacuolevesicle


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. . . developing since 10/06/06