Catalytic activity: ATP + a protein = ADP + a phosphoprotein.
Enzyme regulation: Inhibited by 2-(1-ethyl-2-hydroxyethylamino)-6- benzylamino-9-isopropylpurine (roscovitine), 1-isopropyl-4- aminobenzyl-6-ether-linked benzimidazoles, resveratrol, AT-7519 and olomoucine. Activated by CDK5R1 (p35) and CDK5R2 (p39) during the development of the nervous system; degradation of CDK5R1 (p35) and CDK5R2 (p39) by proteasome result in down regulation of kinase activity, during this process, CDK5 phosphorylates p35 and induces its ubiquitination and subsequent degradation. Kinase activity is mainly determined by the amount of p35 available and subcellular location; reversible association to plasma membrane inhibits activity. Long-term inactivation as well as CDK5R1 (p25)-mediated hyperactivation of CDK5 triggers cell death. The pro-death activity of hyperactivated CDK5 is suppressed by membrane association of CDK5, via myristoylation of p35. Brain-derived neurotrophic factor, glial-derived neurotrophic factor, nerve growth factor (NGF), retinoic acid, laminin and neuregulin promote activity. Neurotoxicity enhances nuclear activity, thus leading to MEF2 phosphorylation and inhibition prior to apoptosis of cortical neurons. Repression by GSTP1 via p25/p35 translocation prevents neurodegeneration.
Subunit structure: Heterodimer composed of a catalytic subunit CDK5 and a regulatory subunit CDK5R1 (p25) and macromolecular complex composed of at least CDK5, CDK5R1 (p35) and CDK5RAP1 or CDK5RAP2 or CDK5RAP3. Only the heterodimer shows kinase activity. Under neurotoxic stress and neuronal injury conditions, p35 is cleaved by calpain to generate p25 that hyperactivates CDK5, that becomes functionally disabled and often toxic. Found in a trimolecular complex with CABLES1 and ABL1. Interacts with CABLES1 and CABLES2 (By similarity). Interacts with AATK and GSTP1. Binds to HDAC1 when in complex with p25. Interaction with myristoylation p35 promotes CDK5 association with membranes. Both isoforms 1 and 2 interacts with beta-catenin/CTNNB1. Interacts with delta- catenin/CTNND2 and APEX1. Interacts with P53/TP53 in neurons. Interacts with EPHA4; may mediate the activation of NGEF by EPHA4. Interacts with PTK2/FAK1 (By similarity).
Subcellular location: Isoform 1: Cytoplasm. Cell membrane; Peripheral membrane protein. Perikaryon. Cell projection, lamellipodium (By similarity). Cell projection, growth cone (By similarity). Cell junction, synapse, postsynaptic cell membrane, postsynaptic density (By similarity). Note=In axonal growth cone with extension to the peripheral lamellipodia (By similarity). Under neurotoxic stress and neuronal injury conditions, CDK5R (p35) is cleaved by calpain to generate CDK5R1 (p25) in response to increased intracellular calcium. The elevated level of p25, when in complex with CDK5, leads to its subcellular misallocation as well as its hyperactivation. Co-localizes with CTNND2 in the cell body of neuronal cells, and with CTNNB1 in the cell-cell contacts and plasma membrane of undifferentiated and differentiated neuroblastoma cells. Reversibly attached to the plasma membrane in an inactive form when complexed to dephosphorylated p35 or CDK5R2 (p39), p35 phosphorylation releases this attachment and activates CDK5.
Isoform 2: Nucleus.
Tissue specificity: Isoform 1 is ubiquitously expressed. Accumulates in cortical neurons (at protein level). Isoform 2 has only been detected in testis, skeletal muscle, colon, bone marrow and ovary.
Post-translational: Phosphorylation on Tyr-15 by ABL1 and FYN, and on Ser-159 by casein kinase 1 promotes kinase activity. By contrast, phosphorylation at Thr-14 inhibits activity.
Phosphorylation at Ser-159 is essential for maximal catalytic activity.
Sequence similarity: Belongs to the protein kinase superfamily. CMGC Ser/Thr protein kinase family. CDC2/CDKX subfamily.
Contains 1 protein kinase domain.C
General information above from UniProt