Thesis Defence: Development of an Affinity-Guided Probe with Turn-On Fluorescence to Selectively Label Kainate Receptors

Anthony Tardif, supervised by Dr. Frederic Menard, will defend their thesis titled “Development of an Affinity-Guided Probe with Turn-On Fluorescence to Selectively Label Kainate Receptors” in partial fulfillment of the requirements for the degree of Master of Science in Chemistry.

An abstract for Anthony Tardif’s thesis is included below.

Defences are open to all members of the campus community as well as the general public. Registration is not required for in person defences.

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ABSTRACT

Kainate receptors (KARs) are classified as one of three main subfamilies of ionotropic glutamate receptors (iGluRs) located in the brain. They have been shown to participate in neurological homeostasis and normal brain development processes such as synapse elimination; however, excessive synapse elimination is a hallmark of neurodegenerative diseases. Despite a strong association between KARs and neurodegeneration, our understanding of the underlying mechanisms that contribute to excessive synapse elimination is hindered by the lack of chemical tools required to study them. The development of new chemical tools to study KARs will provide a better understanding of their role in neurodegenerative processes and help identify therapeutics to treat related symptoms and diseases. This thesis details the synthesis of a fluorescent kainate probe that selectively labels KARs to address this knowledge gap. The kainate probe consists of three smaller molecules; a kainoid ligand, a linker, and a squaraine fluorophore which were all individually synthesized and then coupled to assemble the probe.

Chapter 1 provides a brief introduction to kainate receptors and their role in the brain, as well as an overview of fluorescent protein imaging methods and the concept of turn-on fluorescence. Chapter 2 reviews the structural features that are essential to designing kainoid ligands, precedents in the kainoid syntheses, and the synthesis of a novel kainoid analog, (4R)-4-azidokainic acid, to enable late-stage derivatization at the C4 position of kainic acid. Chapter 3 contextualizes the biological applications of squaraine dyes and how they can be utilized to achieve turn-on fluorescence with improved contrast during fluorescent imaging. Next, it describes the syntheses of squaraine and aminosquaraine intermediates, along with an alkyne linker. Chapter 3 concludes with a detailed account of the synthetic steps performed and the challenges faced towards assembling the kainate probe.

Overall, the synthesis of a novel kainoid analog, (4R)-4-azidokainic acid, serves as a versatile kainoid intermediate, with late-stage modularity, for the development of new kainate probes. The synthetic routes established in Chapter 3 constitute significant progress towards a unique kainate probe with selective turn-on fluorescence to study kainate receptors.