Protein serine/threonine kinases (E.C. 2.7.1.-)

Overview: Protein serine/threonine kinases use the co-substrate ATP to phosphorylate serine and/or threonine residues on target proteins. Most inhibitors of these enzymes have been assessed in cell-free investigations and so may appear to ‘lose’ potency and selectivity in intact cell assays. In particular, ambient ATP concentrations may be influential in responses to inhibitors, since the majority are directed at the ATP binding site (Davies et al., 2000).

It is beyond the scope of the Guide to list all protein kinase activities; this summary focusses on protein kinases involved in signalling from 7-transmembrane receptors.

Nomenclature	Protein kinase A	Protein kinase B	Protein kinase G	Rho kinase
Preferred abbreviation	PKA	PKB	PKG	–
Other names	Cyclic AMP-dependent protein kinase	Akt	Cyclic GMP-dependent protein kinase	P160ROCK, Rho-activated kinase
Ensembl ID	Regulatory subunits: PRKAR1A (ENSG00000108946); PRKAR1B (ENSG00000188191); PRKAR2A (ENSG00000114302); PRKAR2B (ENSG00000005249); Catalytic subunits: PRKACA (ENSG00000072062); PRKACB (ENSG00000142875); PRKACG (ENSG00000165059)	AKT1 (ENSG00000142208); AKT2 (ENSG00000105221); AKT3 (ENSG00000117020)	PRKG1 (ENSG00000185532); PRKG2 (ENSG00000138669)	ROCK1 (ENSG00000067900); ROCK2 (ENSG00000134318)
Endogenous activator	cAMP	PDK1 (Alessi et al., 1997)	cGMP	Rho
Selective activators	N6-Benzyl-cAMP (Christensen et al., 2003)	–	–	–
Selective inhibitors	Rp-cAMPS	–	Rp-8-CPT-cGMPS (Butt et al., 1994)	Y27362 (Uehata et al., 1997), fasudil (Asano et al., 1989)
Probes	[3H]-cAMP	–	–	–

PKA is a heterotetrameric enzyme composed of two regulatory and two catalytic subunits, which can be distinguished from Epac (exchange protein directly activated by cAMP, de Rooij et al., 1998) by differential activation by N⁶-benzyl-cAMP and CPT-2′OMe-cAMP, respectively (Kang et al., 2005). AKT1 and AKT2 can be selectively inhibited by AKT 1/2 inhibitor with pIC₅₀ values of 7.3 and 6.8, respectively (Zhao et al., 2005), while deguelin API2 (Yang et al., 2004), SH5 (Kozikowski et al., 2003) and Akt inhibitor IV (Kau et al., 2003) can inhibit PKB activity by inhibiting activation by upstream kinases.

Protein kinase C

Protein kinase C is the target for the tumour-promoting phorbol esters, such as tetradecanoyl-β-phorbol acetate (TPA).

Classical protein kinase C isoforms: Members of the classical protein kinase C family are activated by Ca²⁺ and diacylglycerol, and may be inhibited by GF109203X, calphostin C, Gö6983, chelerythrine and Ro318220.

Nomenclature	PKCα	PKCβ1	PKCβ2	PKCγ
Other names	PRKCA	PRKCB1	PRKCB2	PRKCG
Ensembl ID	ENSG00000154229	ENSG00000166501	ENSG00	ENSG00000126583
Selective inhibitors	–	Ruboxistaurin (8.3, Jirousek et al., 1996), CGP53353 (6.4, Chalfant et al., 1996)	Ruboxistaurin (8.2, Jirousek et al., 1996)	–

Novel protein kinase C isoforms: Members of the classical protein kinase C family are activated by diacylglycerol and may be inhibited by calphostin C, Gö6983 and chelerythrine.

Nomenclature	PKCδ	PKCε	PKCη	PKCθ	PKCµ
Other names	PRKCD	PRKCE	PRKCH	PRKCQ	KPCD1, nPKC-D1, protein kinase D
Ensembl ID	ENSG00000163932	ENSG00000171132	ENSG00000027075	ENSG00000065675	ENSG00000184304

Atypical protein kinase C isoforms

Nomenclature	PKCζ	PKCι	PKN
Other names	PRKCZ	PRKCI (PKCλ in rodents)	PRK, Protein kinase N1, protein kinase C-related kinase 1
Ensembl ID	ENSG00000067606	ENSG00000163558	ENSG00000123143
Endogenous activator	Arachidonic acid	–	Rho, PIP3

Mitogen-activated protein kinases (MAP kinases)

MAP kinases (CMGC kinases, ENSF00000000137) may be divided into three major families: ERK1/2, JNK and p38 MAP kinases.

Nomenclature	ERK1	ERK2	JNK1	JNK2	JNK3
HUGO Nomenclature	MAPK3	MAPK1	MAPK8	MAPK9	MAPK10
Other names	Insulin-stimulated MAP2 kinase, ERT2, p44-MAPK, Microtubule- associated protein-2 kinase	Mitogen-activated protein kinase 2, p42-MAPK, ERT1	SAPK1, c-Jun N-terminal kinase 1, JNK-46	c-Jun N-terminal kinase 2, JNK-55	c-Jun N-terminal kinase 3, MAP kinase p49 3F12
Ensembl ID	ENSG00000102882	ENSG00000100030	ENSG00000107643	ENSG00000050748	ENSG00000109339
Endogenous activator	MAP2K1, MAP2K2	MAP2K1, MAP2K2	MAP2K4, MAP2K7	MAP2K4, MAP2K7	MAP2K4, MAP2K7
Selective inhibitors			SP600125 (6.7, Bennett et al., 2001)	SP600125 (6.7, Bennett et al., 2001)	SP600125 (6.7, Bennett et al., 2001)

The inhibitors PD98059 (Alessi et al., 1995; Dudley et al., 1995) and U0126 (Duncia et al., 1998; Favata et al., 1998) are used as selective inhibitors of ERK1 and ERK2, but have been shown rather to target the upstream kinase cascade (Davies et al., 2000).

Nomenclature	p38α	p38β	p38γ	p38δ
HUGO Nomenclature	MAPK14	MAPK11	MAPK12	MAPK13
Other names	Cytokine suppressive anti-inflammatory drug binding protein, MAX-interacting protein 2	p38-2, SAPK2	ERK-6, ERK5, SAPK3	SAPK4
Ensembl ID	ENSG00000112062	ENSG00000185386	ENSG00000188130	ENSG00000156711
Endogenous activator	MAP2K3, MAP2K6	MAP2K3, MAP2K6	MAP2K3, MAP2K6	MAP2K3, MAP2K6
Selective inhibitors	SB203580 (8.0, Eyers et al., 1998)	SB202190 (Lee et al., 1994), SB203580 (7.0, Eyers et al., 1998)	–	–

Selected other protein kinase activities

Nomenclature	AMP kinase	Casein kinase 2	Myosin light chain kinase	Calmodulin-dependent kinase II
Preferred abbreviation	AMPK	CK2	MLCK1 (smooth muscle and non-muscle isoform), MLCK2 (skeletal muscle isoform)	CaMKII
Other names	–	EC 2.7.11.1	MYLK	–
Ensembl ID	α1 (ENSG00000132356); α2 (ENSG00000162409); β1 (ENSG00000111725); β2 (ENSG00000131791); γ1 (ENSG00000181929), γ2 (ENSG00000106617); γ3 (ENSG00000115592)	α ENSG00000101266; α′ ENSG00000070770; β ENSG00000204435	MLCK1 ENSG00000065534; MLCK2 ENSG00000101306	α (ENSG00000070808); β (ENSG00000058404); γ (ENSG00000148660); δ (ENSG00000145349)
Endogenous activator	AMP	–	Ca2+-calmodulin	Ca2+-calmodulin
Selective activators	AICA-riboside (Corton et al., 1995)	–	–	–
Selective inhibitors	–	DRB (Zandomeni et al., 1986)	–	K252a (Hashimoto et al., 1991)

AMP-activated protein kinase is a heterotrimeric protein kinase, made up of α, β and γ subunits, while casein kinase 2 is a heterotetrameric protein kinase, made up of 2 β subunits with two other subunits of α and/or α′ composition. STO609 is an inhibitor of calmodulin kinase kinase (Tokumitsu et al., 2002), an upstream activator of calmodulin-dependent kinase.

Glossary

Abbreviations:

AICA-riboside

5-aminoimidazole-4-carboxamide-1-β-riboside, also known as acadesine

AKT1/2

1,3-dihydro-1-(1-[{4-(6-phenyl-1H-imidazo[4,5-g]quinoxalin-7-yl)phenyl}methyl]-4-piperidinyl)-2H-benzimidazol-2-one trifluoroacetate salt hydrate

Akt inhibitor IV

5-(2-benzothiazolyl)-3-ethyl-2-(2-[methylphenylamino]ethenyl)-1-phenyl-1H-benzimidazolium iodide

API2

1,5-dihydro-5-methyl-1-β-D-ribofuranosyl-1,4,5,6,8-pentaazaacennaphthylen-3-amine, also known as triciribine

CGP53353

5,6-bis([4-fluorophenyl]amino)-2H-isoindole-1,3-dione

CPT-2′-OMe-cAMP

8-(4-chlorophenylthio)-2′-O-methyladenosine 3′,5′-cyclic monophosphate monosodium hydrate

DRB

5,6-dichloro-1-β-D-ribofuranosylbenzimidazole

fasudil

1-(5-isoquinolinylsulfonyl)homopiperazine dihydrochloride, also known as HA1077

PD98059

2-(2-amino-3-methoxy-phenyl)chromen-4-one

PDK1

phosphoinoisitide-dependent protein kinase 1 (ENSG00000152256)

Rp-8-CPT-cGMPS

Rp-8-[(4-chlorophenyl)thio]-guanosine-cyclic 3′,5′-hydrogen phosphorothioate

ruboxistaurin

(S)-13-[(dimethylamino)methyl]-10,11,14,15-tetrahydro-4,9:16,21-dimetheno-1H,13H-dibenzo[e,k]pyrrolo[3,4-h][1,4,13]oxadiazacyclohexadecene-1,3(2H)-dione, also known as LY333531

SB203580

4-(5-[4-fluorophenyl]-2-[4-methylsulfinylphenyl]-3H-imidazol-4-yl)pyridine

SP600125

anthra[1,9-cd]pyrazol-6(2H)-one

SH5

STO609, trans-4-[(1R)-1-aminoethyl]-N-4-pyridinyl-cyclohexane carboxamide (Y-27632), and 7-oxo-7H-benzimidazo (2,1a) benz (de) isoquinoline-3-carboxy acid acetate

Further Reading

Akritopoulou-Zanze I, Hajduk PJ (2009). Kinase-targeted libraries: the design and synthesis of novel, potent, and selective kinase inhibitors. Drug Discov Today14: 291–297.

Barnett ME, Madgwick DK, Takemoto DJ (2007). Protein kinase C as a stress sensor. Cell Signal19: 1820–1829.

Borders AS, de AL, Van Eldik LJ, Watterson DM (2008). The p38alpha mitogen-activated protein kinase as a central nervous system drug discovery target. BMC Neurosci9(Suppl. 2) : S12.

Boutros T, Chevet E, Metrakos P (2008). Mitogen-activated protein (MAP) kinase/MAP kinase phosphatase regulation: roles in cell growth, death, and cancer. Pharmacol Rev60: 261–310.

Brown MD, Sacks DB (2008). Compartmentalised MAPK pathways. Handb Exp Pharmacol186: 205–235.

Brown MD, Sacks DB (2009). Protein scaffolds in MAP kinase signalling. Cell Signal21: 462–469.

Burke RE (2007). Inhibition of mitogen-activated protein kinase and stimulation of Akt kinase signaling pathways: Two approaches with therapeutic potential in the treatment of neurodegenerative disease. Pharmacol Ther114: 261–277.

Chene P (2008). Challenges in design of biochemical assays for the identification of small molecules to target multiple conformations of protein kinases. Drug Discov Today13: 522–529.

Clark JE, Sarafraz N, Marber MS (2007). Potential of p38-MAPK inhibitors in the treatment of ischaemic heart disease. Pharmacol Ther116: 192–206.

Coulombe P, Meloche S (2007). Atypical mitogen-activated protein kinases: structure, regulation and functions. Biochim Biophys Acta1773: 1376–1387.

Cuenda A, Rousseau S (2007). p38 MAP-kinases pathway regulation, function and role in human diseases. Biochim Biophys Acta1773: 1358–1375.

Duronio V (2008). The life of a cell: apoptosis regulation by the PI3K/PKB pathway. Biochem J415: 333–344.

Goldstein DM, Gray NS, Zarrinkar PP (2008). High-throughput kinase profiling as a platform for drug discovery. Nat Rev Drug Discov7: 391–397.

Hofmann F, Bernhard D, Lukowski R, Weinmeister P (2009). cGMP regulated protein kinases (cGK). Handb Exp Pharmacol : 137–162.

Ji RR, Suter MR (2007). p38 MAPK, microglial signaling, and neuropathic pain. Mol Pain3: 33.

Johnson GL, Nakamura K (2007). The c-jun kinase/stress-activated pathway: regulation, function and role in human disease. Biochim Biophys Acta1773: 1341–1348.

Johnson L (2007). Protein kinases and their therapeutic exploitation. Biochem Soc Trans35: 7–11.

Kondoh K, Nishida E (2007). Regulation of MAP kinases by MAP kinase phosphatases. Biochim Biophys Acta1773: 1227–1237.

Krishna M, Narang H (2008). The complexity of mitogen-activated protein kinases (MAPKs) made simple. Cell Mol Life Sci65: 3525–3544.

Lawrence MC, Jivan A, Shao C, Duan L, Goad D, Zaganjor E et al. (2008). The roles of MAPKs in disease. Cell Res18: 436–442.

Liao JJ (2007). Molecular recognition of protein kinase binding pockets for design of potent and selective kinase inhibitors. J Med Chem50: 409–424.

Malemud CJ (2007). Inhibitors of stress-activated protein/mitogen-activated protein kinase pathways. Curr Opin Pharmacol7: 339–343.

Manning BD, Cantley LC (2007). AKT/PKB signaling: navigating downstream. Cell129: 1261–1274.

May LT, Hill SJ (2008). ERK phosphorylation: spatial and temporal regulation by G protein-coupled receptors. Int J Biochem Cell Biol40: 2013–2017.

Meloche S, Pouyssegur J (2007). The ERK1/2 mitogen-activated protein kinase pathway as a master regulator of the G1- to S-phase transition. Oncogene26: 3227–3239.

Prudent R, Cochet C (2009). New protein kinase CK2 inhibitors: jumping out of the catalytic box. Chem Biol16: 112–120.

Roberts PJ, Der CJ (2007). Targeting the Raf-MEK-ERK mitogen-activated protein kinase cascade for the treatment of cancer. Oncogene26: 3291–3310.

Rozengurt E (2007). Mitogenic signaling pathways induced by G protein-coupled receptors. J Cell Physiol213: 589–602.

Sale EM, Sale GJ (2008). Protein kinase B: signalling roles and therapeutic targeting. Cell Mol Life Sci65: 113–127.

Sharma V, Wang Q, Lawrence DS (2008). Peptide-based fluorescent sensors of protein kinase activity: design and applications. Biochim Biophys Acta1784: 94–99.

Shaul YD, Seger R (2007). The MEK/ERK cascade: from signaling specificity to diverse functions. Biochim Biophys Acta1773: 1213–1226.

Steinberg GR, Jorgensen SB (2007). The AMP-activated protein kinase: role in regulation of skeletal muscle metabolism and insulin sensitivity. Mini Rev Med Chem7: 519–526.

Tarrant MK, Cole PA (2009). The chemical biology of protein phosphorylation. Annu Rev Biochem78: 797–825.

Towler MC, Hardie DG (2007). AMP-activated protein kinase in metabolic control and insulin signaling. Circ Res100: 328–341.

Turk BE (2008). Understanding and exploiting substrate recognition by protein kinases. Curr Opin Chem Biol12: 4–10.

Ubersax JA, Ferrell JE (2007). Mechanisms of specificity in protein phosphorylation. Nat Rev Mol Cell Biol8: 530–541.

Wagner EF, Nebreda AR (2009). Signal integration by JNK and p38 MAPK pathways in cancer development. Nat Rev Cancer9: 537–549.

Witczak CA, Sharoff CG, Goodyear LJ (2008). AMP-activated protein kinase in skeletal muscle: from structure and localization to its role as a master regulator of cellular metabolism. Cell Mol Life Sci65: 3737–3755.

Zhang J, Yang PL, Gray NS (2009). Targeting cancer with small molecule kinase inhibitors. Nat Rev Cancer9: 28–39.

Zhang Y, Dong C (2007). Regulatory mechanisms of mitogen-activated kinase signaling. Cell Mol Life Sci64: 2771–2789.