Regulation of membrane association and kinase activity of Cdk5–p35 by phosphorylation of p35

Abstract

Although protein kinase Cdk5-p35 is important in many aspects of the development and function of the central nervous system, relatively little is known about its regulation. In the present study, we examined the relationship between the association of this kinase with membranes and its activity in perinatal and adult rat brains. Cdk5-p35 in perinatal brain exhibited higher activity than that found in adult tissue. Gel filtration chromatography revealed that a portion of Cdk5-p35 from fetal brain occurred as a soluble complex, whereas Cdk5-p35 in adult brain occurred predominantly as a membrane-bound complex. Furthermore, soluble Cdk5-p35 in perinatal brain displayed elevated kinase activity, whereas membrane-bound Cdk5-p35 was highly active only in the presence of detergent. This more active soluble form of Cdk5-p35 correlated to a form in which p35 was phosphorylated, whereas the less active membrane-bound form of Cdk5 correlated to the dephosphorylated form of p35, as evidenced by a downward shift in electrophoretic mobility. Cdk5 activity and transition from soluble to membrane-associated compartments could be modulated by conditions that affected the phosphorylation or dephosphorylation of p35. For example, dephosphorylation of p35 in brain extracts was suppressed by selective inhibition of protein phosphatase-1. Together, these results suggest that the kinase activity of Cdk5-p35 is regulated through its association with membranes, which in turn is under the control of Cdk5-dependent phosphorylation and protein phosphatase-1-dependent dephosphorylation of p35.

Cyclin-dependent Kinase-5 Is a Key Molecule in Tumor Necrosis Factor-α-induced Insulin Resistance

“…Although Src family and Abl-tyrosine kinases are potential upstream kinases responsible for CDK5 Tyr-15 phosphorylation (28), we have been unable to detect any TNF-␣-dependent increases in these kinases (data not shown). Alternatively, it is possible that TNF-␣ activates other CDK5-tyrosine kinases, inhibits CDK5 phosphatases, or that the p35 regulatory subunit either enhances CDK5 as a kinase substrate or reduces it as phosphatase substrate in a manner analogous to the 5Ј-adenosine monophosphate-activated protein kinase (29). In any case, the TNF-␣-induced CDK Tyr-15 phosphorylation was dependent upon the MEK/Erk pathway, as the specific MEK inhibitor (PD98059) prevented the TNF-␣-induced increase in p35 expression and CDK tyrosine phosphorylation.…”

The Kinase Activity of Cdk5 and Its Regulation

“…This is particularly useful for looking at the kinase activity in vivo or in cells. The electrophoretic upward mobility of p35 changes gradually to downward during brain development , indicating that the kinase activity of Cdk5-p35 is high in fetal brain and low in adult brain, as has been recently shown (Sato et al 2007a). …”

“…Thus, the membrane association of Cdk5-p35 is regulated by phosphorylation of p35. The soluble, active Cdk5-p35 in fetal brain becomes the membrane-bound and latent complex after dephosphorylation with protein phosphatase 1 (Sato et al 2007a). This evidence shows that the kinase activity of Cdk5 is regulated through its association with membranes, which in turn is under the control of Cdk5-dependent phosphorylation and protein phosphatase-1-dependent dephosphorylation of p35.…”

Orphan kinases turn eccentric

“…After binding to and activating CDK5, p35 becomes phosphorylated by CDK5, causing p35 to dissociate again from CDK5. Subsequently, phospho-p35 either remains membrane-tethered 60 or becomes rapidly degraded in the cytoplasm. 61 Thus, CDK5 is regulated by an ultra-short negative feedback loop.…”