Cell death Flashcards
How many neurons are lost in development?
50%
Where does cell death occur?
It occurs all over the CNS and PNS and it is not confined to a specific area
Neuron survival can be correlated with what?
The size of the tissue
If the structures are larger there is less death
How does neuron cell death occur?
Most die through apoptosis
Describe apoptosis
It is an active process
It is inhibited by actinomycin D (transcription) and cycloheximide (protein synthesis)
If Neuron growth factor is blocked then cells will not grow but if it is blocked and cycloheximide is added they will grow
How are dead neurons cleaned up?
Tidy removal of dying cells is carried out by macrophages
Neuritic disintegration and removal occurs also
Caspases cleave proteins involved in what?
Inhibiting apoptosis
DNA repair
The cell cycle
Nuclear structure
What happens in the intrinsic pathway?
Caused by DNA damage and p53 The mitochondria releases cytochrome c This activates initator caspase 9 This activates caspase 3 apoptosis occurs
What happens in the extrinsic pathway?
Death ligands bind to death receptors
This initates caspase 8
This initates caspase 3
Apoptosis occurs
FAS proteins and ligands play a role in what?
The extrinsic apoptosis pathway
What are the mammalian homologues of ced’s seen in the c.elegans?
Caspases
In c.elegans cells expressing both ced-3 and ced-4 do what?
Die - both must be expressed to die
What is ced-9?
An antiapoptotic gene
What is the hypothesis on how neurons survive?
The targets secrete a factor required for presynaptic neuron servival
What are proneurotophins?
Synthesised in prepro form
The pre-portion is a signal peptide
The pro-portion is cleaved after release
