Integration of lipid and protein kinase signalling in primary cilia biology
Lead Research Organisation:
University College London
Department Name: Oncology
Abstract
This proposal will investigate PI 3-kinases (PI3Ks in short) that regulate fundamental processes in cells. Our laboratory has played a leading role in finding out the roles of the different PI3K family members in the body, how they work and how drugs against some of them can be developed to treat human disease in which PI3K is deregulated. Inhibitors against PI3K family members, including a PI3K family member we discovered, are now approved for the treatment of leukaemia and breast cancer.
Our studies focus on the so-called class I PI3K family members which have been extensively studied and implicated in disease, including in cancer and overgrowth syndromes, which are a group of diseases where different body tissues become large and abnormal, often including the blood vessels.
Despite extensive of research, key elements of PI3K biology are poorly understood, in part because we believe their function has not been investigated in the appropriate conditions and models. Our proposal focuses on a much-overlooked organelle in cells, called the primary cilium. This is a small antenna-like structure that projects out of each cell to sense the environment and is important for development and normal adult cell and tissue function.
Recent studies including our preliminary experiments investigating PI3K in relevant cell conditions have identified a new function for these proteins in controlling the primary cilium. The lipid that class I PI3Ks produce (known as PIP3) localises to primary cilia. However, it remains unknown which class I PI3K(s) are important for this PIP3 and how PI3Ks and PIP3 control cilia function. We will investigate these fundamental biological questions using well-established primary cilia model systems in which we have previous experience, then explore if our findings relate to overgrowth syndromes and may help to treat this condition.
We believe our findings have the potential to uncover insight into long-standing questions in cilia biology and help to understand how increased activity of PI3K contributes to disease, including overgrowth syndromes. Understanding the mechanistic basis of disease informs and is essential for the process of drug/medicine development. Overgrowth conditions are poorly treated and disease mechanisms we identify may show how already existing drugs can be used in these conditions but also reveal new drug targets for development.
Our studies focus on the so-called class I PI3K family members which have been extensively studied and implicated in disease, including in cancer and overgrowth syndromes, which are a group of diseases where different body tissues become large and abnormal, often including the blood vessels.
Despite extensive of research, key elements of PI3K biology are poorly understood, in part because we believe their function has not been investigated in the appropriate conditions and models. Our proposal focuses on a much-overlooked organelle in cells, called the primary cilium. This is a small antenna-like structure that projects out of each cell to sense the environment and is important for development and normal adult cell and tissue function.
Recent studies including our preliminary experiments investigating PI3K in relevant cell conditions have identified a new function for these proteins in controlling the primary cilium. The lipid that class I PI3Ks produce (known as PIP3) localises to primary cilia. However, it remains unknown which class I PI3K(s) are important for this PIP3 and how PI3Ks and PIP3 control cilia function. We will investigate these fundamental biological questions using well-established primary cilia model systems in which we have previous experience, then explore if our findings relate to overgrowth syndromes and may help to treat this condition.
We believe our findings have the potential to uncover insight into long-standing questions in cilia biology and help to understand how increased activity of PI3K contributes to disease, including overgrowth syndromes. Understanding the mechanistic basis of disease informs and is essential for the process of drug/medicine development. Overgrowth conditions are poorly treated and disease mechanisms we identify may show how already existing drugs can be used in these conditions but also reveal new drug targets for development.
Technical Summary
Primary cilia are antenna-like organelles which are critical for cell signalling during development and homeostasis and are deregulated in hereditary diseases called ciliopathies. The mechanisms regulating cilia function and assembly/disassembly dynamics remain incompletely understood. The PIP3 lipid localises to the cilia transition zone but the role it plays, mechanisms by which it functions and how it is produced at this site are poorly characterised. Class I PI 3-kinases (PI3Ks) generate PIP3 to regulate cell growth, proliferation and migration and have been extensively linked to disease including overgrowth syndromes. We have discovered that the class I PI3Ks contribute to the PIP3 pool at the transition zone.
We aim to elucidate which class I PI3K(s) are required for transition zone PIP3 production and uncover the mechanism of action of transition zone PIP3 by:
1. Determining the PI3K isoform responsible for transition zone PIP3
2. Defining the consequences of PI3K activation on cilia signalling
3. Elucidating the role PIP3 plays in transition zone barrier function
4. Understanding the molecular mechanism by which increased cilia-associated PIP3 induces cilia disassembly
Experimentally this will involve:
1.Cilia model systems:
a. Assessing the effect of class I PI3K isoform specific inactivation/inhibition of ciliary PIP3 levels
b. Assessment of cilia signalling output and crosstalk with PI3K
c. Identification and characterisation of PIP3 regulated proteins at the transition zone
d. Identification of key pathways involved in serum-induced cilia disassembly
e. Assessment of signalling downstream of PIP3 in cilia disassembly
2.PIK3CA mutant vascular malformation model systems
a. Analysis of cilia assembly/disassembly dynamics
b. Investigation of relevant targets identified in the cilia model systems
Our proposal has the clear potential to increase the knowledge of fundamental processes in cell biology and disease
We aim to elucidate which class I PI3K(s) are required for transition zone PIP3 production and uncover the mechanism of action of transition zone PIP3 by:
1. Determining the PI3K isoform responsible for transition zone PIP3
2. Defining the consequences of PI3K activation on cilia signalling
3. Elucidating the role PIP3 plays in transition zone barrier function
4. Understanding the molecular mechanism by which increased cilia-associated PIP3 induces cilia disassembly
Experimentally this will involve:
1.Cilia model systems:
a. Assessing the effect of class I PI3K isoform specific inactivation/inhibition of ciliary PIP3 levels
b. Assessment of cilia signalling output and crosstalk with PI3K
c. Identification and characterisation of PIP3 regulated proteins at the transition zone
d. Identification of key pathways involved in serum-induced cilia disassembly
e. Assessment of signalling downstream of PIP3 in cilia disassembly
2.PIK3CA mutant vascular malformation model systems
a. Analysis of cilia assembly/disassembly dynamics
b. Investigation of relevant targets identified in the cilia model systems
Our proposal has the clear potential to increase the knowledge of fundamental processes in cell biology and disease