Protein kinase regulatory subunit

Fig. 4.6. Autoradiograph of a sodium dodecyl sulfate-polyacrylamide gel showing the selective incorporation of 8-NrcAMP into protein kinase regulatory subunit. Protein kinase, prior to irradiation, was incubated with 0.2 pM [-12P]8-N3-cAMP in 50 mM sodium morpho-linoethanesulfonate (pH 6.2), with 10 pM amounts of the indicated unlabeled nucleotides or adenosine (Ade). In the last lane of the gel was the regulatory subunits of the protein kinase which was endogenously phosphory lated with [y- ,2P] ATP. Each lane of the gel contained 40 pg of total protein. The amounts of [32P]8-N,cAMP incorporated into the regulatory subunit were (in fmoles per lane) with no addition 110 + cAMP, < 1 + ATP, 93 ADP, 93 + 5 -AMP, 106 + unlabeled 8-NrcAMP, < 1 + adenosine, 77. (From Pomerantz et al.,...

Biondi, R. M., Baehler, P.J., Reymond, C. D., andVeron, M. (1998). Random insertion of GFP into the cAMP-dependent protein kinase regulatory subunit from Didyostelium discoideum. Nucleic Adds Res., 26, 4946-4952. 

Tyrosine phosphorylated IRS interacts with and activates PI 3-kinase [3]. Binding takes place via the SRC homology 2 (SH2) domain of the PI 3-kinase regulatory subunit. The resulting complex consisting of INSR, IRS, and PI 3-kinase facilitates interaction of the activated PI 3-kinase catalytic subunit with the phospholipid substrates in the plasma membrane. Generation of PI 3-phosphates in the plasma membrane reemits phospholipid dependent kinases (PDKl and PDK2) which subsequently phosphorylate and activate the serine/threonine kinase Akt (synonym protein... 

A protein inhibitor of cyclic AMP-activated protein kinase has been isolated from mammalian tissue and this promotes a five-fold increase in the binding constant of cyclic AMP to protein kinase [79]. The inhibitor is assumed to interact with the catalytic subunit at the regulatory subunit binding site. Thus, inhibitor protein and regulatory subunit modulate the catalytic subunit activity by an identical mechanism. However, it may be more complex, as a protein kinase modulator protein has been isolated which alters the substrate specificity both of cyclic AMP and of cyclic GMP-activated protein kinases, increasing the phosphorylation of some protein substrates and decreasing that of others [80]. 

NEMO kinase (regulatory subunit IKKy), NFkB (nuclear factor kappa B lymphoma) essential modulator, inhibitor of kappa kinase gamma (IKKy). Protein kinase C-interacting protein p62/sequestosome-l, is activated by interleukin IL-IP in sequence, it activates of nuclear factor NFkB in TNFa-stimulated cells (Zotti T et al Mol Immunol 2014 58 27-31). NEMO promotes vFFlP (Fas-associated death domain-like interleukin-1-converting enzyme inhibitory protein) expression by Kaposi sarcoma associated herpesvirus (KSHV) (Tolani B et al J Virol 2014 March 26 PMID 24672029). 

FIGURE 15.7 Cyclic AMP-dependent protein kinase (also known as PKA) is a 150- to l70-kD R9C9 tetramer in mammalian cells. The two R (regulatory) subunits bind cAMP ( = 3 X 10 M) cAMP binding releases the R subunits from the C (catalytic) subunits. C subunits are enzymatically active as monomers. 

AMP-activated protein kinases are heterotrimeric complexes comprised of catalytic a subunits and regulatory (3 and y subunits (Table 1). Each subunit is encoded by at least two genes, some of which can also be subject to alternate splicing, leading to a diverse array of possible heterotrimeric combinations. 

Insulin Receptor. Figure 1 Structure and function of the insulin receptor. Binding of insulin to the a-subunits (yellow) leads to activation of the intracellular tyrosine kinase ((3-subunit) by autophosphorylation. The insulin receptor substrates (IRS) bind via a phospho-tyrosine binding domain to phosphorylated tyrosine residues in the juxtamembrane domain of the (3-subunit. The receptor tyrosine kinase then phosphorylates specific tyrosine motifs (YMxM) within the IRS. These tyrosine phosphorylated motifs serve as docking sites for some adaptor proteins with SRC homology 2 (SH2) domains like the regulatory subunit of PI 3-kinase. 

Protein kinase A (PKA) is a cyclic AMP-dependent protein kinase, a member of a family of protein kinases that are activated by binding of cAMP to their two regulatory subunits, which results in the release of two active catalytic subunits. Targets of PKA include L-type calcium channels (the relevant subunit and site of phosphorylation is still uncertain), phospholam-ban (the regulator of the sarcoplasmic calcium ATPase, SERCA) and key enzymes of glucose and lipid metabolism. 

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