The gamma subunit of the rod photoreceptor cGMP phosphodiesterase can modulate the proteolysis of two cGMP binding cGMP-specific phosphodiesterases (PDE6 and PDE5) by caspase-3.
We have investigated whether the proteolysis of members of the cGMP binding phosphodiesterases (PDE6, PDE5A1, and PDE10A2) by caspase-3 is modulated by the gamma inhibitor subunit of PDE6. We show here that purified caspase-3 proteolyses PDE6, an enzyme composed of two nonidentical catalytic subunits (termed alpha and beta) with molecular mass of 88 and 84 kDa. The proteolysis of PDE6 produced a single fragment with a molecular mass of 78 kDa. This corresponds to the possible cleavage of the caspase-3 consensus DFVD site (amino acids: 164-168) in the alpha subunit and leads to a 50% decrease in the cGMP hydrolysing activity of the enzyme. The addition of rod PDEgamma to the incubation completely blocked the cleavage of PDE6 by caspase-3. In contrast, rod PDEgamma converted PDE5A1 (molecular mass of 98 kDa) to a better substrate for caspase-3. This resulted in the formation of four major fragments with molecular mass of 82-83, 67, 43, and 34 kDa. In addition, caspase-3 induced an approximately 80% reduction in the activity of a partially purified preparation of PDE5A1 in the presence of rod PDEgamma. Caspase-3 also cleaved PDE10A2 (molecular mass of 95 kDa) to a single 48-kDa fragment. This was consistent with cleavage of the DLFD site (amino acids: 312-315) in PDE10A2. In contrast with both PDE6 and PDE5A1, rod PDEgamma was without effect on this enzyme. These data show that rod PDEgamma interacts with at least two members of the cGMP binding PDE family (PDE5A1 and PDE6) and can exert differential effects on the cleavage of these enzymes by caspase-3.
Frame
M
M
Department of Physiology and Pharmacology, Strathclyde Institute for Biomedical Sciences, University of Strathclyde, 27 Taylor Street, Glasgow G4 ONR, UK.
Wan
K F
KF
Tate
R
R
Vandenabeele
P
P
Pyne
N J
NJ
D015106:3',5'-Cyclic-GMP Phosphodiesterases / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology*; D000818:Animals; D001483:Base Sequence; D053148:Caspase 3; D020169:Caspases / Q000494:pharmacology*; D006152:Cyclic GMP / Q000378:metabolism*; D054706:Cyclic Nucleotide Phosphodiesterases, Type 5; D054707:Cyclic Nucleotide Phosphodiesterases, Type 6; D004347:Drug Interactions; D008168:Lung / Q000201:enzymology; D008297:Male; D051379:Mice; D008969:Molecular Sequence Data; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism*; D012313:RNA / Q000096:biosynthesis; D012374:Rod Cell Outer Segment / Q000201:enzymology*; D012689:Sequence Homology, Nucleic Acid; D013737:Testis / Q000201:enzymology
D012313:RNA; C492284:Pde10a protein, mouse; D010727:Phosphoric Diester Hydrolases; D015106:3',5'-Cyclic-GMP Phosphodiesterases; D054706:Cyclic Nucleotide Phosphodiesterases, Type 5; D054707:Cyclic Nucleotide Phosphodiesterases, Type 6; C517382:Pde5a protein, mouse; C517438:Pde6b protein, mouse; C505409:Casp3 protein, mouse; D053148:Caspase 3; D020169:Caspases; D006152:Cyclic GMP