Date of Award

5-2021

Degree Type

Thesis

Degree Name

Honors Thesis

Department

Biology

First Advisor

Jennifer R. Kowalski

Abstract

Millions of neurons in our bodies relay messages to various organ systems. Neuronal signaling involves a combination of electrical and chemical signals between neurons that create responses in the receiving neuron that are either inhibitory or excitatory. The nervous system relies on the balance between excitatory and inhibitory signaling (E:I balance) to maintain its function. G protein-coupled receptors (GPCRs) are cell surface proteins that play critical roles in regulating neuronal signaling by binding molecules that initiate intracellular relay pathways. One conserved GPCR known as FSHR-1, homologous to human follicle stimulating hormone (FSH) receptor, regulates neuromuscular signaling in Caenorhabditis elegans roundworms. The specific location(s) where fshr-1 is expressed to regulate normal neuromuscular signaling, as well as the ligand molecule that activates the FSHR-1 receptor signaling, are still unknown.

My first project (Chapter 2) investigates where fshr-1 expression is sufficient to restore wild type muscle contraction rates to fshr-1-deficient mutants. Based on previous behavioral and imaging data, I hypothesized that fshr-1 acts in one or more neurons to promote muscle contraction. To test this hypothesis, I used a thrashing assay to determine where fshr-1 is sufficient to restore neuromuscular signaling. My results showed that fshr-1 can act in cholinergic and GABA neurons, as well as in the intestine, to promote wild type muscle contractions in normal growth conditions. Future experimentation will be required to see how fshr-1 acts to regulate neuromuscular signaling in diverse physiologic conditions, as well as in other neuronal subclasses.

My second project (Chapter 3) investigates the relevant molecules that bind extracellularly to FSHR-1 to help initiate its signaling pathways. Human FSHR, analogous to C. elegans FSHR-1, is regulated by binding of FSH alpha () and beta (β) molecules; however, there are no direct FSH orthologs in the worm. I hypothesized that FSHR-1 binds one or more extracellular ligands, likely a glycopeptide or neuropeptide, because such molecules regulate human FSHR and/or control neuromuscular signaling. I have begun to test this hypothesis by amplifying the extracellular domain (ECD) of the FSHR-1 receptor in C. elegans and expressing it as a protein in yeast cells. Eventually, the purified FSHR-1ECD protein will be used to probe a pool of worm proteins and, using mass spectrometry, identify potential proteins that bind and activate FSHR-1 signaling in the worm.

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