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Researchers discover new signalling pathway regulating blood vessel growth

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28 October 2010

Researchers at the Babraham Institute (an institute of BBSRC) have discovered a previously unknown signalling pathway that controls the formation and remodelling of blood vessels - a process called angiogenesis. The research, published this week in Science Signalling, reveals that a signalling protein called Arap3 is vital for establishing a circulatory system to nourish the developing embryo. Mice lacking Arap3 die before birth because of the failure to 'sprout' new blood vessels during embryonic development, a process orchestrated by a family of proteins called phosphoinositide 3-kinases (PI3Ks) which regulate Arap3.

While angiogenesis occurs during growth and development, it also serves to repair and rebuild blood vessels in adults after injury and in wound healing. Understanding how these processes normally work therefore gives us a chance to work out what is happening when things go wrong. Angiogenesis also occurs in many pathological situations like cancer - tumours need a blood supply to obtain oxygen and nutrients. Age-related macular degeneration (AMD) is another condition involving aberrant growth of blood vessels, which causes irreversible loss of vision in the elderly. The identification of a novel player in these pathways, and greater understanding of the mechanisms underpinning angiogenesis, therefore opens up the possibility of innovative drug targets for anti-angiogenic and pro-angiogenic therapies.

'Cascades' of signalling proteins communicate messages within a cell, or from one cell to its neighbours, to co-ordinate the development of an organism from an embryo. Arap3, which was discovered at Babraham, is an important signalling protein that regulates angiogenesis and is itself controlled by another signalling protein called phosphoinositide 3-kinase (PI3K). Arap3 in turn regulates two signalling proteins called RhoA and Arf6, which are important for cell motility, a crucial aspect of angiogenesis.

The lead author, Dr Sonja Vermeren explained, "We discovered that Arap3 is needed for angiogenesis when we studied a mouse lacking Arap3 and found that the embryos died because they didn't form blood vessels correctly. Instead of an organised network of capillaries, the circulatory system of these embryos was highly disorganised. Remodelling of the primitive vascularisation had not progressed in an orderly fashion. The formation of new 'sprouts' during angiogenesis is a dynamic process that goes wrong when Arap3 is missing."

PI3Ks are involved in a diverse range of activities inside cells, such as cell proliferation, motility and survival, which are central to angiogenesis. PI3Ks generate a lipid signalling molecule called phosphatidylinositol 3,4,5-trisphosphate, known as PIP3 for short, which localises to the inside of the outer cell membrane and activates PI3K effectors. About 50 PI3K effectors have been identified, which bind to and are regulated by PIP3. Arap3 is one such effector. Its unique binding specificity to and regulation by PIP3 may make it a suitable target for anti-angiogenic therapies.

The paper showed that 'sprouting angiogenesis' is particularly affected by loss of Arap3 and points to a previously unknown signalling pathway that controls developmental angiogenesis immediately downstream of the PI3K signalling protein, through Arap3 to Rho and Arf family small GTPases (key regulators of cellular events such as cell migration). The Babraham Institute, an institute of the Biotechnology and Biological Sciences Research Council (BBSRC) where the research was conducted, is a centre for studying the basic biology of signalling inside and between cells, supporting BBSRC's mission to drive advances in fundamental bioscience to underpin pharmaceuticals and wellbeing. Results from these investigations, supported by both BBSRC and MRC (Medical Research Council), are contributing greater understanding to the processes through which angiogenesis occurs and may provide a rationale for the development of therapies to treat angiogenesis-based diseases.

ENDS

Notes to editors

Publication details: L. Gambardella, M. Hemberger, B. Hughes, E. Zudaire, S. Andrews, S. Vermeren, (2010) PI3K signaling through the dual GTPase-activating protein ARAP3 is essential for developmental angiogenesis. Sci. Signal. 3, ra76 (2010). DOI: 10.1126/scisignal.2001026.

About the Babraham Institute

The Babraham Institute is an institute of the Biotechnology and Biological Sciences Research Council (BBSRC) located near Cambridge, undertaking international quality research to support the biomedical aspects of the BBSRC's mission. The Institute's research is focused on understanding the biological events that underlie the normal functions of cells and the implication of failure or abnormalities in these processes. The latest technologies are being used to study the basis of conditions such as neurodegenerative disorders, birth defects, cancer and diseases of the immune and cardiovascular systems. With a strategic focus on 'healthy ageing', novel approaches for tackling chronic diseases and public health concerns like obesity and inflammatory disorders are being discovered. www.babraham.ac.uk

About BBSRC

BBSRC is the UK funding agency for research in the life sciences. Sponsored by Government, BBSRC annually invests around £470M in a wide range of research that makes a significant contribution to the quality of life in the UK and beyond and supports a number of important industrial stakeholders, including the agriculture, food, chemical, healthcare and pharmaceutical sectors.

BBSRC provides institute strategic research grants to the following:

  • The Babraham Institute
  • Institute for Animal Health
  • Institute of Biological, Environmental and Rural Sciences (Aberystwyth University)
  • Institute of Food Research
  • John Innes Centre
  • The Genome Analysis Centre
  • The Roslin Institute (University of Edinburgh)
  • Rothamsted Research

The Institutes conduct long-term, mission-oriented research using specialist facilities. They have strong interactions with industry, Government departments and other end-users of their research.