To obtain the full sequence of the recently identified new ryanodine receptor (RYR) and inositol 1,4,5-trisphosphate receptor (IP3R).
To completely screen the expression of all known RYR- and IP3R-isoforms in normal brain and in tissues and cells from patients with neurological disorders.
To determine how these receptors function to gate Ca2+ in neuronal tissues.
To understand the role of RYRs and IP3Rs for brain function.
Ca2+ is an important intracellular messenger in brain. There are 2 intracellular channels responsible for releasing stored Ca2+: RYRs and IP3Rs. A further exploration of the role of these internal receptors in brain is urgently needed since these channels are the targets of neurotransmitter receptors involved in cognitive processes of long-term potentiation, long-term depression and spatial and motor learning. Alterations in the IP3 signalling pathway may contribute to e.g. Alzheimer's disease and manic-depressive illness. Also RYRs may be involved in abnormal brain function as malignant hyperthermia susceptible pigs express a mutant RYR in the brain as well as in skeletal muscle and are highly susceptible to stress. Considering the central role of these internal receptors in so many aspects of brain function, it is surprising that so little is known about their basic properties in brain. The current project therefore aims to understand the distribution, structure and physiology of the RYRs and IP3Rs in normal and abnormal brain function.
To determine how these receptors function to gate Ca2+ in neuronal tissues, we will focus on Ca2+ and cyclic ADP-ribose (cADPR). Ca2+ is an activator of both RYRs and IP3Rs. We will establish whether all members of both receptor families behave similarly and the mode of activation will be characterised at the protein level. cADPR is a newly described messenger for RYR activation. How is its intracellular concentration regulated in brain cells ? Which members of the RYR family are gated and how does cADPR interact at the molecular level ? 'Quantal' Ca2+ release is a property of brain IP3Rs. Also RYRs exhibit this property. The mechanism for this behaviour and its functional significance will be explored.
To understand the role of RYRs and IP3Rs for brain function, brain cells expressing RYRs at detectable levels will be screened for responses to caffeine, ryanodine and cADPR. Endogenous RYRs will be eliminated and cells that do not express endogenous RYRs will be transfected with RYRs or mutated forms to study intracellular Ca2+ homeostasis. The brain of transgenic mice lacking RYR3 will be screened for alterations in Ca2+ homeostasis and functions depending on Ca2+ signalling. The study will also be conducted at the level of IP3Rs using the molecular tools that will become available as the project progresses. Brain cells containing both receptors will be used to understand how both interact to generate the complex signalling patterns during brain activation.
Funding SchemeCSC - Cost-sharing contracts
CB2 3EJ Cambridge
OX1 3QT Oxford