Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels are expressed in neurons of the central and peripheral nervous system, and underlie the hyperpolarizationactivated current (Ih). Through control of basic membrane properties, HCN channels and Ih play roles in automaticity as well as synaptic integration and neuronal input-output properties. Thus, Ih contributes to neuronal circuits underlying processes such as sleep and learning and memory, and potentially participates in the pathophysiology of neurological disorders such as epilepsy and chronic pain. Because small changes in HCN channel and Ih properties have significant impact on a given circuit, it is critical to determine what role regulatory mechanisms may play in vivo to modify channel function. In these studies, we examined the role of the tetratricopeptide repeatcontaining Rab8b-interacting protein, TRIP8b, in HCN channel and I h expression, trafficking, and function. TRIP8b interacts with all known HCN channel subunits, and colocalizes with HCN1 in distal dendrites of neocortical and CA1 hippocampal pyramidal neurons. Thus, we hypothesized it may be an important regulator of HCN channels in the mammalian brain.
In these studies, we characterized how TRIP8b regulates HCN channel expression and localization, as well as Ih biophysical properties in both in vitro and in vivo systems. In chapter two, we show that TRIP8b is alternatively spliced at the N-terminus, and different splice isoforms differentially control Ih current amplitude and biophysical properties, as well as HCN channel trafficking to the cellular surface. In chapter three, we characterize a mouse with genetic deletion of TRIP8b and demonstrate that expression of Ih in hippocampal CA1 pyramidal neurons in vivo requires TRIP8b. This loss of I h is due to decreased HCN channel expression on the surface of the neuronal plasma membrane due to impaired trafficking. We also show that mice lacking TRIP8b demonstrate antidepressant behavior. In chapter four, we further examine the interaction between HCN channels and TRIP8b and potential methods for its regulation. This work identifies TRIP8b as a key molecular regulator of HCN channels and Ih in vivo, and suggests that the interaction may be a useful target for future therapies involving HCN channels and Ih.
|Advisor:||Chetkovich, Dane M.|
|Commitee:||Awatramani, Raj, Kessler, John A., Miller, Richard J.|
|Department:||Neuroscience Institute Graduate Program|
|School Location:||United States -- Illinois|
|Source:||DAI-B 71/12, Dissertation Abstracts International|
|Subjects:||Molecular biology, Neurosciences|
|Keywords:||Channel trafficking, Depression, Hcn channels, Hippocampus, Hyperpolarization-activated current, Trip8b|
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