Project group leader Camilla RaiborgProtein dynamics in tumor suppressor pathways

The transformation of a healthy cell into a cancer cell requires multiple events. Knowing the players involved in the processes that regulate cell growth, survival, differentiation, cell division and cell death, can in turn allow us to establish new strategies for diagnosis and treatment of cancers.  In our research we focus on protein complexes that shape cellular membranes or alter cellular signalling and in this way contribute to tumour suppression or cancer development. Our aim is to uncover novel cellular mechanisms that can be exploited in cancer medicine.

 

ESCRTs - endosomal protein complexes required for transport

Nutrients and macromolecules are taken up by cells into small vesicles called endosomes.The endocytic pathway communicates with other membrane-systems in the cell by extensive vesicular transport of membranes and macromolecules between the different compartments. This vesicle traffic serves as a fundamental basis for maintaining cell function and homeostasis, such as nutrient status and signalling output from activated growth factor receptors. Upon activation, signalling receptors are internalized and degraded by the endocytic pathway and this constitutes an important mechanism to attenuate receptor signalling, thus preventing overgrowth. Receptor downregulation is mediated by a huge array of protein complexes commonly known as endosomal protein complexes required for transport (ESCRT). Work from our lab has contributed strongly to the current status of the field. Since the discovery of the ESCRT machinery in 2001/2002, it was not until recently that we’re beginning to understand how components of the ESCRT pathway can serve as prognostic and diagnostic tools in cancer. And still our lab is discovering new ESCRT functions in different cancer relevant cellular processes, lastly in resealing of the nuclear envelope after mitosis. Although we know the constituents of the ESCRT machinery, we completely lack the understanding of how these proteins dynamically work together. In our project group, we have recently obtained groundbreaking new information about this, using cutting edge live-imaging of fluorescently tagged ESCRT-proteins, making ESCRT research one of our main focus areas.

 

Endosomes containing internalized epidermal growth factor (white)

 

ER-endosome contact sites

Although the endocytic pathway has been extensively studied for several decades, very little is known about the direct communication between endosomes and the endoplasmic reticulum (ER). In our project group, we have recently identified the basic molecular machinery responsible for the formation of a novel type of ER-endosome contact. We have shown that the spatial proximity of ER and endosomes results in translocation of endosomes to the plasma membrane, where the vesicles fuse with the plasma membrane to form cellular protrusions. This opens up for extensive experimentation on cancer related processes, such as receptor downregulation, autophagy and cell migration. We will continue to explore the composition and function of this new type of contact sites as one of our main focus areas.

 

A PC12 cell stimulated with NGF uses late endosomes (red) to grow protrusions. The endoplasmatic reticulum is shown in green.

 

Cover of November edition of Molecular Cancer Research 2015 by Thorvaldsen, Pedersen, Wenzel et al.

3D structured illumination micrograph of SW480 colon carcinoma cells showing Tankyrase-inhibitor induced degradasomes.

 

Link to popular scientific article in Norwegian:

http://forskning.no/celler-kreft/2016/01/filmer-levende-kreftceller

 

 

Our research is supported by :                

 

Coworkers:

 Nina Marie Pedersen

 Ling Wang

 

Key publications ESCRTs:

Vietri M, Schink KO, Campsteijn C, Wegner CS, Schultz S, Christ L, Thoresen SB, Brech A, Raiborg C and Stenmark H. (2015) Spastin and ESCRT-III coordinate mitotic spindle disassembly and nuclear envelope sealing. Nature. Jun 11;522(7555):231-5

          - Comment in Sundquist WI and Ullman KS. (2015) An ESCRT to seal the envelope. Science.  Jun 19;348(6241)

          - Comment in Burk B. (2015) Nuclear dilemma resolved. Nature. Jun 11;522(7555)

          - This article was recommended by the Faculty of 1000: http://f1000.com/prime/725533850

 

Raiborg C and Stenmark, H. (2009) The ESCRT machinery in endosomal sorting of ubiquitylated membrane proteins. Nature. Mar 26;458(7237):445-52.

 

Raiborg C, Malerød L, Pedersen NM, Stenmark H. (2008) Differential functions of Hrs and ESCRT proteins in endocytic membrane trafficking. Exp Cell Res. Feb 15;314(4):801-13.

             - Cover on Exp Cell Res2009 on line edition.

Raiborg C, Wesche J, Malerod L, Stenmark H. (2006) Flat clathrin coats on endosomes mediate degradative protein sorting by scaffolding Hrs in dynamic microdomains. J Cell Sci. Jun 15;119:2414-24

Raiborg C, Rusten TE, Stenmark H. (2003) Protein sorting into multivesicular endosomes. Curr. Opin. Cell Biol. Aug;15(4):446-55.

Raiborg C, Bache KG, Gillooly DJ, Madshus IH, Stang E, Stenmark H. (2002) Hrs sorts ubiquitinated proteins into clathrin-coated microdomains of early endosomes. Nat Cell Biol. 4:394-8.

              - Comment in Clague MJ. (2002) Membrane transport: a coat for ubiquitin. Curr. Biol. 12: 529-31.

              - Comment in Finly D. (2002) Ubiquitin chained and crosslinked. Nat. Cell. Biol. 4: 121-3.

 Raiborg C, Bache KG, Mehlum A, Stang E, Stenmark H. (2001) Hrs recruits clathrin to early endosomes. EMBO J. 20(17):5008-21.

 Raiborg C,Bremnes B, Mehlum A, Gillooly DJ, D'Arrigo A, Stang E, Stenmark H. (2001) FYVE and coiled-coil domains determine the specific localisation of Hrs to early endosomes. J Cell Sci.. 114(12):2255-63.

 

Key publications ER-endosome contact sites:

Raiborg C, Wenzel EM and Stenmark H. (2015) ER-endosome contact sites: molecular compositions and functions. EMBO J. Jul 14;34(14):1848-58

Raiborg C*, Wenzel EM, Pedersen NM, Olsvik H,  Schink KO, Schultz SW,  Vietri M, Nisi V, Bucci C, Brech A, Johansen T and Stenmark H*. (2015) Repeated ER-endosome contacts promote endosome translocation and neurite outgrowth. Nature. Apr 9;520(7546):234-8   * Corresponding authors

              - Comment in Krauss and Haucke. (2015) A grab to move on: ER-endosome contacts in membrane   protrusion formation and neurite outgrowth. EMBO J. Jun 3;34(11):1442-4

              - Comment in Wijdeven RH et al.,(2015) ER contact sites direct late endosome transport. Bioessays 37 in press.

              - This article was recommended by the Faculty of 1000: http://f1000.com/prime/725428494