Alpha-fodrin is cleaved by caspase-3 in a chronic ocular hypertensive (COH) rat model of glaucoma.
OBJECTIVE
alpha-Fodrin is a neuronal cytoskeletal protein and a known caspase-3 target. We sought to determine whether caspase-3 cleaves alpha-fodrin in COH rat retinas and whether this process is reduced by adeno-associated virus (AAV)-induced retinal ganglion cell expression of baculovirus inhibitory repeat-containing 4 (BIRC4), a potent caspase-3 inhibitor.


METHODS
Ocular hypertension was induced unilaterally in five rat eyes by limbal injection of hypertonic saline. In a similar experiment, ocular hypertension was induced in four eyes pre-treated with an intravitreal injection of AAV-BIRC4 to assess alpha-fodrin cleavage. Western immunoblotting was performed on all retinas.


RESULTS
Caspase-3 cleavage of alpha-fodrin yields a specific 120kDa protein fragment. COH retina immunoblots indicated significantly more caspase-3 cleavage of alpha-fodrin than controls (P < 0.01, paired t-test). Inhibition of retinal caspase-3 activity with BIRC4 reduced caspase-3-mediated alpha-fodrin cleavage compared to controls.


CONCLUSIONS
This confirms our previous finding of caspase-3 cleavage of alpha-fodrin in COH retinas and parallels pathology seen in Alzheimer's disease, in which neurons undergo chronic caspase activation, slow build-up of cleavage products, and delayed apoptosis. If caspase activation in glaucoma leads to protracted rather than rapid retinal ganglion cell apoptosis, a much longer therapeutic window exists for apoptosis inhibition with caspase inhibitors such as BIRC4.
Tahzib
N G
NG
Department of Ophthalmology, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, Mail Code 6230, San Antonio, TX 78229-3900, USA.
Ransom
N L
NL
Reitsamer
H A
HA
McKinnon
S J
SJ
D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism*; D053148:Caspase 3; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism*; D002908:Chronic Disease; D004195:Disease Models, Animal; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005901:Glaucoma / Q000201:enzymology / Q000378:metabolism*; D006868:Hydrolysis; D008840:Microfilament Proteins / Q000378:metabolism*; D009798:Ocular Hypertension / Q000201:enzymology / Q000378:metabolism*; D011506:Proteins / Q000494:pharmacology; D051381:Rats; D011914:Rats, Inbred BN; D051636:X-Linked Inhibitor of Apoptosis Protein; D013049:Spectrin
D002352:Carrier Proteins; D053148:Caspase 3; D061945:Caspase Inhibitors; D020169:Caspases; D004791:Enzyme Inhibitors; D008840:Microfilament Proteins; D011506:Proteins; D051636:X-Linked Inhibitor of Apoptosis Protein; D013049:Spectrin; C505410:Casp3 protein, rat