Caspase-9 (ICE, LAP6, Mch6, Apaf-3) (CASP9) Antibody – Rabbit Polyclonal

This gene encodes a member of the cysteine-aspartic acid protease (caspase) family. Sequential activation of caspases plays a central role in the execution-phase of cell apoptosis. Caspases exist as inactive proenzymes which undergo proteolytic processing at conserved aspartic residues to produce two subunits, large and small, that dimerize to form the active enzyme. This protein can undergo autoproteolytic processing and activation by the apoptosome, a protein complex of cytochrome c and the apoptotic peptidase activating factor 1; this step is thought to be one of the earliest in the caspase activation cascade. This protein is thought to play a central role in apoptosis and to be a tumor suppressor. Alternative splicing results in multiple transcript variants. [provided by RefSeq, May 2013]

Function: Involved in the activation cascade of caspases responsible for apoptosis execution. Binding of caspase-9 to Apaf-1 leads to activation of the protease which then cleaves and activates caspase-3. Promotes DNA damage-induced apoptosis in a ABL1/c-Abl-dependent manner. Proteolytically cleaves poly(ADP-ribose) polymerase (PARP). Ref.17 Ref.24Isoform 2 lacks activity is an dominant-negative inhibitor of caspase-9. Ref.17 Ref.24

Catalytic activity: Strict requirement for an Asp residue at position P1 and with a marked preference for His at position P2. It has a preferred cleavage sequence of Leu-Gly-His-Asp-|-Xaa. Ref.24

Enzyme regulation: Inhibited by the effector protein NleF that is produced by pathogenic E.coli; this inhibits apoptosis. Ref.24

Subunit structure: Heterotetramer that consists of two anti-parallel arranged heterodimers, each one formed by a 35 kDa (p35) and a 10 kDa (p10) subunit. Caspase-9 and APAF1 bind to each other via their respective NH2-terminal CED-3 homologous domains in the presence of cytochrome C and ATP. Interacts (inactive form) with EFHD2. Interacts with HAX1. Interacts with BIRC2/c-IAP1, XIAP/BIRC4, BIRC5/survivin, BIRC6/bruce and BIRC7/livin. Interacts with ABL1 (via SH3 domain); the interaction is direct and increases in the response of cells to genotoxic stress and ABL1/c-Abl activation. Interacts with NleF from pathogenic E.coli. Ref.16 Ref.17 Ref.18 Ref.20 Ref.22 Ref.24

Tissue specificity: Ubiquitous, with highest expression in the heart, moderate expression in liver, skeletal muscle, and pancreas. Low levels in all other tissues. Within the heart, specifically expressed in myocytes. Ref.18

Developmental stage: Expressed at low levels in fetal heart, at moderate levels in neonate heart, and at high levels in adult heart. Ref.18

Post-translational modification: Cleavages at Asp-315 by granzyme B and at Asp-330 by caspase-3 generate the two active subunits. Caspase-8 and -10 can also be involved in these processing events.Phosphorylated at Thr-125 by MAPK1/ERK2. Phosphorylation at Thr-125 is sufficient to block caspase-9 processing and subsequent caspase-3 activation. Phosphorylation on Tyr-153 by ABL1/c-Abl; occurs in the response of cells to DNA damage. Ref.15 Ref.17

Sequence similarities: Belongs to the peptidase C14A family.Contains 1 CARD domain.