User:Alisa Cario

Introduction and Background

The cytoskeleton brings structure to the cell, is integral in cell division, and aids in migration. One of the constitutive parts of the cytoskeleton are microtubules. Microtubules are polymerized from tubulin subunits that incorporate into a hollow cylindrical structure linked together by lateral and vertical hydrogen bonds. Each tubulin subunit is made from a heterodimer of alpha and beta tubulin. Both alpha and beta tubulin are known to bind to GTP. However, only the beta subunit hydrolyzes GTP, which occurs once incorporated into microtubules. The beta tubulin hydrolysis of GTP to GDP is known to destabilize microtubules. Microtubules have polarity where one end of microtubule, called the plus end, has a greater affinity to add tubulin subunits than the other end, called the minus end. Microtubules are inherently dynamic, going through periods of depolymerization, known as catastrophe, and then return to polymerization, known as rescue. Microtubules can also go through a process called tread milling, where the length of the microtubule does not change but the rate of polymerization at the plus end equals the rate of depolymerization at the minus end. There are a number of microtubule associated proteins (MAPs) that are known to regulate the dynamics of microtubules. Some examples of this include MAPTau, MAP2 and stathmin. See tubulin, tau.

Figure XXX. Stathmin in purple can bind to tubulin dimers to prevent polymerization or to microtubules to increase catastrophe

Function

, also known as oncoprotein 18 or metablastin, is a 19kDa microtubule associated protein known to destabilize microtubules ^[1]. Stathmin is a cell cycle and developmentally regulated protein, known to play a role in proliferation, differentiation, and function of cells ^{[2] [3]}. Stathmin can bind to to inhibit polymerization or it can bind to the microtubule to enhance the rate of catastrophe^[4]

Mitosis: Stathmin's role in the cell cycle progression is well characterized. During interphase, microtubules are relatively stable. However during the onset of mitosis, stathmin is upregulated to increase the rate of catastrophe of microtubules, causing them to become more dynamic. Stathmin has also been shown to bind and sequester two tubulin heterodimers, reducing the amount of available tubulin to polymerize microtubules ^[5]. However, as mitosis progresses, microtubules must repolymerize to form the mitotic spindle. Stathmin is regulated during this process by phosphorylation ^{[6] [7]}. There are four known , serine 16, serine 25, serine 38, and serine 63 ^[8]. Stathmin is the known target of cyclin-dependent kinases ^[9]. Stathmin overexpression prevents mitotic spindle formation where inhibition interferes with later stages in mitosis ((^[10])).

Migration: The cytoskeleton is a vital part of cell migration. The leading edge is driven by actin polymerization ( ). However, microtubules are needed to retract from the trailing edge to move the cell forward. Stathmin is thought to have a role in migration, allowing to microtubules to depolymerize to aid in movement. Stathmin has been show to be a part of the integrin alpha5 beta1/FAK/ ERK pathway ^[11].

Differentiation: Stathmin expression is regulated during stages of development. It is regulated in early and late embryogenesis. ^[12] . It is also regulated in differentiating muscle cells, T lymphocytes, and oligodendryocytes ^{[13] [14]}.

Structural Highlights

How does the structure relate to it's function?

consistis of a coiled coil alpha helix, that binds across two tubulin heterodimers, and a mostly disordered N-terminal region that also has some beta strand properties. These different regions of the protein are known to have different functions.

The is known to increase tubulin catastrophe. This region helps destabilize the ends of the microtubule filaments by curving the tubulin dimers at the end, and disrupting lateral hydrogen bonds. The N-terminal region is known as the regulatory domain of the protein, because it is subject to most of the post-translational modifications. This region binds and caps alpha tubulin to accomplish this task. (Cite error: Invalid <ref> tag;

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The, also known as the interaction domain, is known to sequester tubulin heterodimers. This region is comprised of a . This region of stathmin is . Helix 10 of alpha tubulin is thought to be important for incorporation into microtubules (Cite error: Invalid <ref> tag;

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The structure of stathmin, in 4eb6, is bound to two tubulin heterodimers. The tubulin dimers are bound to outside ligands. is a chemotherapeutic that binds to tubulin to prevent microtubule polymerization ( Cite error: Invalid <ref> tag;

refs with no name must have content). The tubulin subunits are bound to from The beta subunits of tubulin are bound to GDP and each of the alpha subunits are bound to GTP and a Magnesium ion. There are also to the stathmin in this structure. The mutations at position 11 from an cysteine to an alanine and position 16 from a Phenylalanine to a Tryptophan.

Disease relevance

Multiple Schlerosis: Stathmin expression is has been linked to multiple sclerosis (MS) , a neurodegenerative disorder characterized by lack of motor control and numbness. MS is caused by loss of myelination on axons in the nervous system. Myelination of axons is performed by cells called oligodendrocytes. Stathmin is regulated in oligodendrocyte lineage, with progenitor cells containing larger amounts than differentiated oligodendrocytes. Brain tissue samples from people suffering from multiple sclerosis found that stathmin is up regulated later in the lineage of oligodendrocytes. The up-regulation of stathmin showed a more globular morphology of the cells. Oligodendrocyte ability to myelinate axons in the central nervous system was greatly reduced in these patients ^[15].

Cancer: Due to stathmin's role in mitosis and cell migration, it is not surprising that is has been implicated in many cancers and is an active target of cancer therapeutics. Stathmin is defined as an oncoprotein. Overexpression of stathmin has been shown to increase metastasis, worse prognosis, and increased chemoresistance ( Cite error: Invalid <ref> tag;

refs with no name must have content ). Stathmin levels are known to be increasesd in a number of cancers. Stathmin was seen to be upregulated in breast cancer tissue comparative with normal breast tissue ^[16]. Another study was done to show stathmin upregulation in esophageal squamous cell carcinomas <refPMID: 23229199></ref>. Studies using a non-phosphorylatable stathmin mutant shows that cells arrest during mitosis ^[17])

Evolutionary conservation

Stathmin belongs to a gene family that have a characteristic stathmin-like domain spanning across eukaryotes. There are four isoforms of stathmin which are alternatively spliced from a single gene. This family includes Stathmin-1, SCG10/stathmin-2, SCILP/stathmin-3, and RB3/stathmin-4. SCG10 and SCLIP, are exclusively neuronal proteins, while RB3 is expressed mostly in the brain but some in the adrenal glands ^[18]. ^[19]. Unlike the neuronal proteins, stathmin-1 is ubiquitously expressed in all cell types. All members of this family contain the C-terminal coiled coil domain. However, the binding affinity to tubulin of the protein family members differ ^[20]. Interestingly, the neuronal isoforms are known to contain an additional N-terminal domain to affect their localization ^[21].

Links to available structures

• Stathmin SLD domain complex with tubulin

• • 3ryf – rSTM + tubulin + GTP - rat
    
  • 3hkb, 3ryc, 3ryi – rSTM + tubulin + GTP + GDP
    
  • 3ryh – rSTM + tubulin + GTP + phosphomethylphosphonic acid guanylate
    
  • 3hkc, 3n2g, 3n2k – rSTM + tubulin + GTP + GDP + pyridine derivative
    
  • 3hkd – rSTM + tubulin + GTP + GDP + pyrrolidine derivative
    
  • 3hke – rSTM + tubulin + GTP + GDP + benzenesulfonamide derivative
    

• Stathmin SLD domain complex with tubulin and drugs

• • 1sa0 – rSTM + tubulin + GTP + GDP + anti-gout drug
    
  • 1sa1, 1z2b – rSTM + tubulin + GTP + GDP + anti-wart drug
    
  • 5j2u – rSTM (mutant) + tubulin + GTP + GDP + anti-cancer drug
    
  • 3du7 – rSTM + tubulin + GTP + GDP + phomopsine + anti-gout drug
    
  • 3e22 – rSTM + tubulin + GTP + GDP + soblidotine + anti-gout drug
    
  • 5lp6, 5kx5 – rSTM + tubulin + GTP + GDP + drug
    
  • 3ut5 – rSTM (mutant) + tubulin + GTP + GDP + ustiloxine + anti-gout drug + Vinca tetrapeptide
    

• Stathmin SLD domain complex with tubulin and tubulin tyrosine ligase

• • 4iij – rSTM + tubulin + tubulin tyrosine ligase + GTP + GDP
    
  • 4ihj – rSTM + tubulin + tubulin tyrosine ligase + GTP + GDP + ADP
    
  • 5jqg, 4wbn, 4i55 – rSTM + tubulin + tubulin tyrosine ligase + GTP + GDP + ATP derivative
    
  • 4o2a – rSTM + tubulin + tubulin tyrosine ligase + GTP + GDP + ADP + inhibitor
    
  • 4i50 – rSTM + tubulin + tubulin tyrosine ligase + GTP + GDP + epothilone
    
  • 4o4l, 5j2t, 5bmv, 5la6, 5jh7, 5jvd, 5fnv, 5c8y, 5ca0, 5ca1, 5cb4, 4yj2, 4yj3, 4x1i, 4x1k, 4x1y, 4x20, 4tuy, 4zol, 4tv8, 4tv9, 4o4j, 4o4l, 5i50, 4i4t, 4o4i, 4o2l, 5iyz, 5la6, 5m7e, 5m7g, 5m8d, 5m8g, 5xlt – rSTM + tubulin + tubulin tyrosine ligase + GTP + GDP + ATP derivative + anti-cancer drugs
    
  • 4o2b – rSTM + tubulin + tubulin tyrosine ligase + GTP + GDP + ATP derivative + anti-gout drug
    
  • 5lov, 5njh – rSTM + tubulin + tubulin tyrosine ligase + GTP + GDP + ATP derivative + azoamide
    
  • 5lxs, 5lxt – rSTM + tubulin + tubulin tyrosine ligase + GTP + GDP + ATP derivative + discodermolide
    
  • 5lyj, 5mf4 – rSTM + tubulin + tubulin tyrosine ligase + GTP + GDP + ATP derivative + natural product
    
  • 5o7a – rSTM + tubulin + tubulin tyrosine ligase + GTP + GDP + ATP derivative + quinolin derivative
    

References

1. ↑ Belmont LD, Mitchison TJ. Identification of a protein that interacts with tubulin dimers and increases the catastrophe rate of microtubules. Cell. 1996 Feb 23;84(4):623-31. PMID:8598048
2. ↑ Jourdain L, Curmi P, Sobel A, Pantaloni D, Carlier MF. Stathmin: a tubulin-sequestering protein which forms a ternary T2S complex with two tubulin molecules. Biochemistry. 1997 Sep 9;36(36):10817-21. doi: 10.1021/bi971491b. PMID:9312271 doi:http://dx.doi.org/10.1021/bi971491b
3. ↑ Howell B, Larsson N, Gullberg M, Cassimeris L. Dissociation of the tubulin-sequestering and microtubule catastrophe-promoting activities of oncoprotein 18/stathmin. Mol Biol Cell. 1999 Jan;10(1):105-18. PMID:9880330
4. ↑ Belmont LD, Mitchison TJ. Identification of a protein that interacts with tubulin dimers and increases the catastrophe rate of microtubules. Cell. 1996 Feb 23;84(4):623-31. PMID:8598048
5. ↑ Jourdain L, Curmi P, Sobel A, Pantaloni D, Carlier MF. Stathmin: a tubulin-sequestering protein which forms a ternary T2S complex with two tubulin molecules. Biochemistry. 1997 Sep 9;36(36):10817-21. doi: 10.1021/bi971491b. PMID:9312271 doi:http://dx.doi.org/10.1021/bi971491b
6. ↑ Marklund U, Osterman O, Melander H, Bergh A, Gullberg M. The phenotype of a "Cdc2 kinase target site-deficient" mutant of oncoprotein 18 reveals a role of this protein in cell cycle control. J Biol Chem. 1994 Dec 2;269(48):30626-35. PMID:7982983
7. ↑ Labdon JE, Nieves E, Schubart UK. Analysis of phosphoprotein p19 by liquid chromatography/mass spectrometry. Identification of two proline-directed serine phosphorylation sites and a blocked amino terminus. J Biol Chem. 1992 Feb 15;267(5):3506-13. PMID:1737801
8. ↑ Beretta L, Dobransky T, Sobel A. Multiple phosphorylation of stathmin. Identification of four sites phosphorylated in intact cells and in vitro by cyclic AMP-dependent protein kinase and p34cdc2. J Biol Chem. 1993 Sep 25;268(27):20076-84. PMID:8376365
9. ↑ Larsson N, Marklund U, Gradin HM, Brattsand G, Gullberg M. Control of microtubule dynamics by oncoprotein 18: dissection of the regulatory role of multisite phosphorylation during mitosis. Mol Cell Biol. 1997 Sep;17(9):5530-9. PMID:9271428
10. ↑
11. ↑ Lawler S, Gavet O, Rich T, Sobel A. Stathmin overexpression in 293 cells affects signal transduction and cell growth. FEBS Lett. 1998 Jan 2;421(1):55-60. PMID:9462839
12. ↑ Amat JA, Fields KL, Schubart UK. Distribution of phosphoprotein p19 in rat brain during ontogeny: stage-specific expression in neurons and glia. Brain Res Dev Brain Res. 1991 Jun 21;60(2):205-18. PMID:1893566
13. ↑ Filbert EL, Le Borgne M, Lin J, Heuser JE, Shaw AS. Stathmin regulates microtubule dynamics and microtubule organizing center polarization in activated T cells. J Immunol. 2012 Jun 1;188(11):5421-7. doi: 10.4049/jimmunol.1200242. Epub 2012, Apr 23. PMID:22529300 doi:http://dx.doi.org/10.4049/jimmunol.1200242
14. ↑ Liu A, Muggironi M, Marin-Husstege M, Casaccia-Bonnefil P. Oligodendrocyte process outgrowth in vitro is modulated by epigenetic regulation of cytoskeletal severing proteins. Glia. 2003 Dec;44(3):264-74. doi: 10.1002/glia.10290. PMID:14603467 doi:http://dx.doi.org/10.1002/glia.10290
15. ↑ Liu A, Stadelmann C, Moscarello M, Bruck W, Sobel A, Mastronardi FG, Casaccia-Bonnefil P. Expression of stathmin, a developmentally controlled cytoskeleton-regulating molecule, in demyelinating disorders. J Neurosci. 2005 Jan 19;25(3):737-47. doi: 10.1523/JNEUROSCI.4174-04.2005. PMID:15659612 doi:http://dx.doi.org/10.1523/JNEUROSCI.4174-04.2005
16. ↑ Curmi PA, Nogues C, Lachkar S, Carelle N, Gonthier MP, Sobel A, Lidereau R, Bieche I. Overexpression of stathmin in breast carcinomas points out to highly proliferative tumours. Br J Cancer. 2000 Jan;82(1):142-50. doi: 10.1054/bjoc.1999.0891. PMID:10638981 doi:http://dx.doi.org/10.1054/bjoc.1999.0891
17. ↑ Gavet O, Ozon S, Manceau V, Lawler S, Curmi P, Sobel A. The stathmin phosphoprotein family: intracellular localization and effects on the microtubule network. J Cell Sci. 1998 Nov;111 ( Pt 22):3333-46. PMID:9788875
18. ↑ Maucuer A, Moreau J, Mechali M, Sobel A. Stathmin gene family: phylogenetic conservation and developmental regulation in Xenopus. J Biol Chem. 1993 Aug 5;268(22):16420-9. PMID:8344928
19. ↑ Schubart UK, Banerjee MD, Eng J. Homology between the cDNAs encoding phosphoprotein p19 and SCG10 reveals a novel mammalian gene family preferentially expressed in developing brain. DNA. 1989 Jul-Aug;8(6):389-98. PMID:2776625
20. ↑ Charbaut E, Curmi PA, Ozon S, Lachkar S, Redeker V, Sobel A. Stathmin family proteins display specific molecular and tubulin binding properties. J Biol Chem. 2001 May 11;276(19):16146-54. doi: 10.1074/jbc.M010637200. Epub 2001, Feb 15. PMID:11278715 doi:http://dx.doi.org/10.1074/jbc.M010637200
21. ↑ Gavet O, Ozon S, Manceau V, Lawler S, Curmi P, Sobel A. The stathmin phosphoprotein family: intracellular localization and effects on the microtubule network. J Cell Sci. 1998 Nov;111 ( Pt 22):3333-46. PMID:9788875