A Proline-rich Sequence Unique to MEK1 and MEK2 is Required for Raf Binding and Regulates MEK Function

Overview

Journal Mol Cell Biol

Specialty Cell Biology

Date 1995 Oct 1

PMID 7565670

Citations 54

Authors

A D Catling

H J Schaeffer

C W Reuter

G R Reddy

M J Weber

Affiliations

Soon will be listed here.

Abstract

Mammalian MEK1 and MEK2 contain a proline-rich (PR) sequence that is absent both from the yeast homologs Ste7 and Byr1 and from a recently cloned activator of the JNK/stress-activated protein kinases, SEK1/MKK4. Since this PR sequence occurs in MEKs that are regulated by Raf family enzymes but is missing from MEKs and SEKs activated independently of Raf, we sought to investigate the role of this sequence in MEK1 and MEK2 regulation and function. Deletion of the PR sequence from MEK1 blocked the ability of MEK1 to associate with members of the Raf family and markedly attenuated activation of the protein in vivo following growth factor stimulation. In addition, this sequence was necessary for efficient activation of MEK1 in vitro by B-Raf but dispensable for activation by a novel MEK1 activator which we have previously detected in fractionated fibroblast extracts. Furthermore, we found that a phosphorylation site within the PR sequence of MEK1 was required for sustained MEK1 activity in response to serum stimulation of quiescent fibroblasts. Consistent with this observation, we observed that MEK2, which lacks a phosphorylation site at the corresponding position, was activated only transiently following serum stimulation. Finally, we found that deletion of the PR sequence from a constitutively activated MEK1 mutant rendered the protein nontransforming in Rat1 fibroblasts. These observations indicate a critical role for the PR sequence in directing specific protein-protein interactions important for the activation, inactivation, and downstream functioning of the MEKs.

Citing Articles

Exploring the inhibitory potential of xanthohumol on MEK1/2: a molecular docking and dynamics simulation investigation.

Gholizadeh Siahmazgi Z, Irani S, Ghiaseddin A, Soutodeh F, Gohari Z, Afifeh J Res Pharm Sci. 2025; 19(6):669-682.

PMID: 39911899 PMC: 11792713. DOI: 10.4103/RPS.RPS_38_24.

MEK inhibitors in cancer treatment: structural insights, regulation, recent advances and future perspectives.

Ram T, Singh A, Kumar A, Singh H, Pathak P, Grishina M RSC Med Chem. 2023; 14(10):1837-1857.

PMID: 37859720 PMC: 10583825. DOI: 10.1039/d3md00145h.

KLHL7 promotes hepatocellular carcinoma progression and molecular therapy resistance by degrading RASA2.

Chen L, Li Y, Chen Y iScience. 2023; 26(6):106914.

PMID: 37378318 PMC: 10291331. DOI: 10.1016/j.isci.2023.106914.

The mechanism of activation of MEK1 by B-Raf and KSR1.

Maloney R, Zhang M, Liu Y, Jang H, Nussinov R Cell Mol Life Sci. 2022; 79(5):281.

PMID: 35508574 PMC: 9068654. DOI: 10.1007/s00018-022-04296-0.

Ras Isoforms from Lab Benches to Lives-What Are We Missing and How Far Are We?.

Nair A, Kubatzky K, Saha B Int J Mol Sci. 2021; 22(12).

PMID: 34204435 PMC: 8233758. DOI: 10.3390/ijms22126508.

References

Dent P, Chow Y, Wu J, Morrison D, Jove R, Sturgill T . Expression, purification and characterization of recombinant mitogen-activated protein kinase kinases. Biochem J. 1994; 303 ( Pt 1):105-12. PMC: 1137563. DOI: 10.1042/bj3030105. View

Jaiswal R, Moodie S, Wolfman A, Landreth G . The mitogen-activated protein kinase cascade is activated by B-Raf in response to nerve growth factor through interaction with p21ras. Mol Cell Biol. 1994; 14(10):6944-53. PMC: 359225. DOI: 10.1128/mcb.14.10.6944-6953.1994. View

Han J, Lee J, Bibbs L, Ulevitch R . A MAP kinase targeted by endotoxin and hyperosmolarity in mammalian cells. Science. 1994; 265(5173):808-11. DOI: 10.1126/science.7914033. View

Mansour S, Matten W, Hermann A, Candia J, Rong S, Fukasawa K . Transformation of mammalian cells by constitutively active MAP kinase kinase. Science. 1994; 265(5174):966-70. DOI: 10.1126/science.8052857. View

Marshall C . Specificity of receptor tyrosine kinase signaling: transient versus sustained extracellular signal-regulated kinase activation. Cell. 1995; 80(2):179-85. DOI: 10.1016/0092-8674(95)90401-8. View

Catling A, Reuter C, Cox M, Parsons S, Weber M . Partial purification of a mitogen-activated protein kinase kinase activator from bovine brain. Identification as B-Raf or a B-Raf-associated activity. J Biol Chem. 1994; 269(47):30014-21. View

Finney R, Robbins S, Bishop J . Association of pRas and pRaf-1 in a complex correlates with activation of a signal transduction pathway. Curr Biol. 1993; 3(12):805-12. DOI: 10.1016/0960-9822(93)90214-9. View

Zheng C, Guan K . Activation of MEK family kinases requires phosphorylation of two conserved Ser/Thr residues. EMBO J. 1994; 13(5):1123-31. PMC: 394921. DOI: 10.1002/j.1460-2075.1994.tb06361.x. View

Brunet A, Pages G, Pouyssegur J . Growth factor-stimulated MAP kinase induces rapid retrophosphorylation and inhibition of MAP kinase kinase (MEK1). FEBS Lett. 1994; 346(2-3):299-303. DOI: 10.1016/0014-5793(94)00475-7. View

10.

Derijard B, Hibi M, Wu I, Barrett T, Su B, Deng T . JNK1: a protein kinase stimulated by UV light and Ha-Ras that binds and phosphorylates the c-Jun activation domain. Cell. 1994; 76(6):1025-37. DOI: 10.1016/0092-8674(94)90380-8. View

11.

Leevers S, PATERSON H, Marshall C . Requirement for Ras in Raf activation is overcome by targeting Raf to the plasma membrane. Nature. 1994; 369(6479):411-4. DOI: 10.1038/369411a0. View

12.

Ambrosio L, Mahowald A, Perrimon N . Requirement of the Drosophila raf homologue for torso function. Nature. 1989; 342(6247):288-91. DOI: 10.1038/342288a0. View

13.

Dent P, Haser W, Haystead T, Vincent L, Roberts T, Sturgill T . Activation of mitogen-activated protein kinase kinase by v-Raf in NIH 3T3 cells and in vitro. Science. 1992; 257(5075):1404-7. DOI: 10.1126/science.1326789. View

14.

Posada J, Yew N, Ahn N, Woude G, Cooper J . Mos stimulates MAP kinase in Xenopus oocytes and activates a MAP kinase kinase in vitro. Mol Cell Biol. 1993; 13(4):2546-53. PMC: 359584. DOI: 10.1128/mcb.13.4.2546-2553.1993. View

15.

Kolch W, Heidecker G, Lloyd P, Rapp U . Raf-1 protein kinase is required for growth of induced NIH/3T3 cells. Nature. 1991; 349(6308):426-8. DOI: 10.1038/349426a0. View

16.

Tsuda L, Inoue Y, Yoo M, Mizuno M, Hata M, Lim Y . A protein kinase similar to MAP kinase activator acts downstream of the raf kinase in Drosophila. Cell. 1993; 72(3):407-14. DOI: 10.1016/0092-8674(93)90117-9. View

17.

Der C, Finkel T, Cooper G . Biological and biochemical properties of human rasH genes mutated at codon 61. Cell. 1986; 44(1):167-76. DOI: 10.1016/0092-8674(86)90495-2. View

18.

Warne P, Viciana P, Downward J . Direct interaction of Ras and the amino-terminal region of Raf-1 in vitro. Nature. 1993; 364(6435):352-5. DOI: 10.1038/364352a0. View

19.

Heasley L, Johnson G . The beta-PDGF receptor induces neuronal differentiation of PC12 cells. Mol Biol Cell. 1992; 3(5):545-53. PMC: 275607. DOI: 10.1091/mbc.3.5.545. View

20.

Dickson B, Sprenger F, Morrison D, Hafen E . Raf functions downstream of Ras1 in the Sevenless signal transduction pathway. Nature. 1992; 360(6404):600-3. DOI: 10.1038/360600a0. View