Subject Area

Biochemistry, Biological Sciences, General, Biophysics, Biostatistics, Cell Biology, Chemistry

Abstract

PAS domains and Cryptochromes function as sensory and regulatory modules that mediate signal transduction across all domains of life.  Their conserved structural architecture and versatile functionality have made them the focus of mechanistic studies and therapeutic development.  In circadian and light-sensing systems, PAS domains and cryptochrome play critical roles in transducing environmental signals into biological responses.   Here, we examine the signaling pathways of PAS domain containing photoreceptors in plants (Zeitlupe) and fungus (Vivid) and the mammalian Cryptochrome (CRY).

In plants, the circadian clock regulates both long-term developmental processes and daily physiological rhythms.  The blue-light photoreceptor ZTL regulates the circadian clock through light-dependent conformational changes within its LOV domain and is further stabilized by interacting with Gigantea (GI).  Although light induced conformational changes in ZTL have been characterized, the mechanism in which ZTL’s LOV-domain binds to GI remains unclear.  To further understand the protein interaction, an optogenetic tool incorporating key residues involved in complex stabilization was developed.

In mammals, circadian rhythms are governed by transcription-translation feedback loops (TTFLs) composed of core clock proteins including CLOCK, BMAL1, Period (PER), and Cryptochrome (CRY1/CRY2).  Continuous disruption of circadian rhythm adversely affects physical and mental health, motivating the development of small-molecule modulators targeting core clock components.  Specifically, these small molecule modulators compete with endogenous ligands to modulate the circadian rhythm. Recently studies have shown that CRY1 and CRY2 have distinct regulatory roles that are presented by physiological outputs.  Here, we explore CRY-directed small molecule modulators and their effects on glucocorticoid receptor signaling.

Lastly, the signaling mechanism of the Neurospora crassa (N. crassa) VVD homolog in Fusarium oxysporum (FoVVD) was characterized.  Fungal photoadaptation is mediated by blue-light-induced conformational changes that regulate dimerization and are in direct response to environmental stressors such as light and oxidative conditions.  The exact molecular mechanisms these fungal species utilize are not fully understood, but there are two models that have been biophysically characterized.  In N. crassa VVD, a light induced dimerization is exhibited as a rapidly exchanging dimer that is affected by concentration.  In contrast, the VVD homologue ENV1 dimerizes through a disulfide bond in the presence of both light and oxidative stress.  Size exclusion chromatography indicates that FoVVD exhibits similar behavior as seen with VVD and ENV1.  Under oxidative conditions, FoVVD forms a disulfide-linked dimer similar to ENV1, whereas under reducing conditions it forms a rapidly exchanging dimer independent of light, resembling VVD.

Degree Date

Spring 2026

Document Type

Dissertation

Degree Name

Ph.D.

Department

Chemistry

Advisor

Brian Zoltowski

Second Advisor

Alexander Lippert

Third Advisor

Peng Tao

Fourth Advisor

Edward Glasscock

Number of Pages

214

Format

.pdf

Creative Commons License

Creative Commons Attribution-Noncommercial 4.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial 4.0 License

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