| Structural highlights
Disease
MELK_HUMAN Note=Defects in MELK are associated with some cancers, such as brain or breast cancers. Expression is dramatically increased in aggressive undifferentiated tumors, correlating with poor patient outcome in breast and brain cancers, suggesting a role in tumor-initiating cells and proliferation via its function in cell proliferation regulation.
Function
MELK_HUMAN Serine/threonine-protein kinase involved in various processes such as cell cycle regulation, self-renewal of stem cells, apoptosis and splicing regulation. Has a broad substrate specificity; phosphorylates BCL2L14, CDC25B, MAP3K5/ASK1 and ZNF622. Acts as an activator of apoptosis by phosphorylating and activating MAP3K5/ASK1. Acts as a regulator of cell cycle, notably by mediating phosphorylation of CDC25B, promoting localization of CDC25B to the centrosome and the spindle poles during mitosis. Plays a key role in cell proliferation and carcinogenesis. Required for proliferation of embryonic and postnatal multipotent neural progenitors. Phosphorylates and inhibits BCL2L14, possibly leading to affect mammary carcinogenesis by mediating inhibition of the pro-apoptotic function of BCL2L14. Also involved in the inhibition of spliceosome assembly during mitosis by phosphorylating ZNF622, thereby contributing to its redirection to the nucleus. May also play a role in primitive hematopoiesis.[1] [2] [3] [4] [5] [6]
Publication Abstract from PubMed
MELK (maternal embryonic leucine zipper kinase), which is a member of the AMPK (AMP-activated protein kinase)-related kinase family, plays important roles in diverse cellular processes and has become a promising drug target for certain cancers. However, the regulatory mechanism of MELK remains elusive. Here, we report the crystal structure of a fragment of human MELK that contains the kinase domain and ubiquitin-associated (UBA) domain. The UBA domain tightly binds to the back of the kinase domain, which may contribute to the proper conformation and activity of the kinase domain. Interestingly, the activation segment in the kinase domain displays a unique conformation that contains an intramolecular disulfide bond. The structural and biochemical analyses unravel the molecular mechanisms for the autophosphorylation/activation of MELK and the dependence of its catalytic activity on reducing agents. Thus, our results may provide the basis for designing specific MELK inhibitors for cancer treatment.
Structural basis for the regulation of maternal embryonic leucine zipper kinase.,Cao LS, Wang J, Chen Y, Deng H, Wang ZX, Wu JW PLoS One. 2013 Jul 26;8(7):e70031. doi: 10.1371/journal.pone.0070031. Print 2013. PMID:23922895[7]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Seong HA, Gil M, Kim KT, Kim SJ, Ha H. Phosphorylation of a novel zinc-finger-like protein, ZPR9, by murine protein serine/threonine kinase 38 (MPK38). Biochem J. 2002 Feb 1;361(Pt 3):597-604. PMID:11802789
- ↑ Davezac N, Baldin V, Blot J, Ducommun B, Tassan JP. Human pEg3 kinase associates with and phosphorylates CDC25B phosphatase: a potential role for pEg3 in cell cycle regulation. Oncogene. 2002 Oct 31;21(50):7630-41. PMID:12400006 doi:10.1038/sj.onc.1205870
- ↑ Vulsteke V, Beullens M, Boudrez A, Keppens S, Van Eynde A, Rider MH, Stalmans W, Bollen M. Inhibition of spliceosome assembly by the cell cycle-regulated protein kinase MELK and involvement of splicing factor NIPP1. J Biol Chem. 2004 Mar 5;279(10):8642-7. Epub 2003 Dec 29. PMID:14699119 doi:10.1074/jbc.M311466200
- ↑ Mirey G, Chartrain I, Froment C, Quaranta M, Bouche JP, Monsarrat B, Tassan JP, Ducommun B. CDC25B phosphorylated by pEg3 localizes to the centrosome and the spindle poles at mitosis. Cell Cycle. 2005 Jun;4(6):806-11. Epub 2005 Jun 5. PMID:15908796
- ↑ Beullens M, Vancauwenbergh S, Morrice N, Derua R, Ceulemans H, Waelkens E, Bollen M. Substrate specificity and activity regulation of protein kinase MELK. J Biol Chem. 2005 Dec 2;280(48):40003-11. Epub 2005 Oct 10. PMID:16216881 doi:10.1074/jbc.M507274200
- ↑ Lin ML, Park JH, Nishidate T, Nakamura Y, Katagiri T. Involvement of maternal embryonic leucine zipper kinase (MELK) in mammary carcinogenesis through interaction with Bcl-G, a pro-apoptotic member of the Bcl-2 family. Breast Cancer Res. 2007;9(1):R17. PMID:17280616 doi:10.1186/bcr1650
- ↑ Cao LS, Wang J, Chen Y, Deng H, Wang ZX, Wu JW. Structural basis for the regulation of maternal embryonic leucine zipper kinase. PLoS One. 2013 Jul 26;8(7):e70031. doi: 10.1371/journal.pone.0070031. Print 2013. PMID:23922895 doi:10.1371/journal.pone.0070031
|
