Nuclear localization of Cdk5 is a key determinant in the postmitotic state of neurons of neurons Zhang J, Cicero SA, Wang L, Romito ‐ Digiacomo RR, Yang Y, Herrup K. P Proc Natl Acad Sci U S A. 2008 Jun 4;105(25):8772 ‐ 7. N tl A d S i U S A 2008 J 4 105(25) 8772 7 Speaker: Hung ‐ En Hsia Advisor: Chin Tin Chen Ph D Advisor: Chin ‐ Tin Chen Ph.D. Date: May 26 th 2009
Postmitotic state: cell cycle arrest Cell cycle related (p21, cdk5…) neuronal death neuronal death 3. Maturation 2. Migration e.g. A 1. Neurogenesis SVZ, SGZ Herrup K and Yang Y (2007 ) Nat Rev Neurosci. 2
Loss ‐ of ‐ function of cdk5 causes problems Loss of function of cdk5 causes problems • Cdk5 ‐ / ‐ mice – Can not survive after birth – Defects in neural development – Cell cycle related neuronal death (CRND) Cell cycle related neuronal death (CRND) 3
Cyclin ‐ dependent kinase 5 (cdk5) Cyclin dependent kinase 5 (cdk5) • Cyclin ‐ dependent kinase (cdk) – Promote cell cycle progression y p g – Its activation depends on binding of cyclin • Cdk5 is an unique member in cdk family Cdk5 i i b i dk f il – It does not promote cell cycle progression – Its activation does not rely on association of cyclin – It could be activated by its activator: p35 p39 It could be activated by its activator: p35, p39 – Predominately neuronal ‐ specific 4
Functions of cdk5 Functions of cdk5 Dhavan R and Tsai LH (2001) Nat Rev Mol Cell Biol . 5
CDK5 ‐ + Devoid of cdk5 d f dk Overactivation activity of cdk5 6
Overactivation of cdk5 causes problems Overactivation of cdk5 causes problems • Alzheimer’s disease (AD) Alzheimer s disease (AD) – Lost of memory and the ability of remembering recently learned facts recently learned facts – Accumulation of beta ‐ amyloid (A ) – Hyperphosphorylation of tau – Neural degeneration g • p25: generated by proteolytic cleavage of p35 – A more effective activator of cdk5 because its A ff i i f dk b i longer half ‐ life 7
CDK5 CDK5 ‐ + Death of Death of Death of Death of neurons neurons 8
Localization Localization 9
Liver cell PKA 10
Cell lysate Primary neurons Primary neurons culture Different cell cycle activity, different subcellular cdk5 distribution Transgene mouse modals AD patients AD patients 11
The subcellular distribution of cdk5 changes because of different cell cycle activity NIH 3T3 cell lysate Serum Serum cdk5 Serum withdraw → Cell cycle arrest S Serum add ‐ back → Cell cycle re ‐ entry dd b k → C ll l 12
Cell cycle re ‐ entry is accompanied by the loss of nuclear cdk5 (1/2) Mouse cortical neurons primary culture treated with A Cdk5 PCNA (Proliferating Cell Nuclear Antigen) PCNA (Proliferating Cell Nuclear Antigen) 13
Cell cycle re ‐ entry is accompanied by the loss of nuclear cdk5 (2/2) Before A treatment After A treatment Cdk5 Cdk5 BrdU DAPI 14
The quantity of cdk5 is reduced in the nucleus of neurons with cell cycle activity in AD mouse models Alzheimer’s disease Alzheimer s disease mouse model R 1.40 mice carry the entire human beta ‐ amyloid precursor protein (APP) gene on a yeast artificial chromosome i ( ) ifi i l h 15
The localization of cdk5 is responsive to cell cycle activity induced by E2f1 deficiency Cdk5 PCNA PCNA DAPI E2f1 works as a cell cycle suppressor in mature neurons E2f1 works as a cell cycle suppressor in mature neurons. 16
Cdk5 is almost exclusively cytoplasmic in proliferating neurons in AD brain Cdk5 Age matched Age ‐ matched PCNA PCNA control AD patient 17
Blockage of g nuclear export Nuclear distribution of cdk5 blocks cell cycle activity Target cdk5 to nucleus 18
Blockage of cdk5 export could block g p A induced cell cycle activity Leptomycin B (LMB): A nuclear export inhibitor Leptomycin B (LMB): A nuclear export inhibitor 19
Nuclear cdk5 could block cell cycle activity Nuclear cdk5 could block cell cycle activity BrdU Cdk5 ‐ / ‐ Cdk5 / NLS: Nuclear Localization Signal BrdU Cdk5 / Cdk5 ‐ / ‐ NES N NES: Nuclear Export Signal l E t Si l 20
Cell lysate Cell lysate Primary neurons Primary neurons Different cell cycle Nuclear activity, different localization of localization of subcelluar cdk5 subcelluar cdk5 Transgene Transgene Cdk5 is a key distribution mouse modals determinant in the postmitotic the postmitotic AD patients state of neurons Blockage of nuclear export Nuclear distribution of cdk5 blocks cell cycle activity Target cdk5 to nucleus l 21
Proposed models Proposed models Copani A et al ., (2001) Trends Neurosci. Zhang J and Herrup K (2009) Cell Cycle 22
Thanks for your attention! Thanks for your attention! 23
A /oxidative stress…etc. p35 p35 CDK5 CDK5 Ca 2+ Calpain Calpain T 1/2 <20 min p25 p p CDK5 Microtubules Microtubules p p p p T 1/2 <60 min Tau Tau Cell Death 24
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Cdk5 ‐ / ‐ primary cortical neurons Cdk5 / primary cortical neurons 27
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