Investigating The Sensitivity Of Drosophila Cryptochrome To Blue Light And Magnetic Fields.

  • Anna Munro

Student thesis: Phd

Abstract

There is considerable debate over the precise biophysical mechanism mediating the phenomenon of animal magnetosensitivity. The favoured mechanism is a blue light dependent ‘radical pair mechanism’ (RPM), which involves the photoactivation of the blue light sensitive flavoprotein, Cryptochrome (CRY). The photoexcitation of a bound flavin adenine dinucleotide (FAD) cofactor triggers electron transfer from key tryptophan residues in CRY, leaving each partner (CRY and FAD) with an uneven number of electrons: forming a radical pair (RP). Importantly, the radicals which make up this pair have internal properties which can be influenced by an external magnetic field, leading to modulation of downstream activity in a cellular environment. In this thesis, I first explore the possibility of harnessing the magnetosensitivity of CRY to modulate an existing optogenetic tool, the AtCRY2/CIB1 optical dimeriser, using external magnetic fields, with the aim to move towards the development of a CRY based magnetogenetic tool. Secondly, because the canonical RPM cannot explain several behavioural and electrophysiological observations in which mutation of key residues, or protein deletions, do not affect magnetosensitivity, I focus attention to the C-terminal of CRY. I show that expression of the C-terminus of Drosophila CRY is alone sufficient to support magnetosensitivity in a model Drosophila larval motoneuron. Detailed analysis suggests that the C-terminal and full-length CRY may act via different underlying transduction mechanisms contradicting the widely held premise that external magnetic fields act by potentiating the BL-mediated pathway. A better understanding of how the CRY C-terminus supports magnetosensitivity may, in turn, facilitate the design of effective magnetogenetic tools.
Date of Award1 Aug 2023
Original languageEnglish
Awarding Institution
  • The University of Manchester
SupervisorForbes Manson (Supervisor) & Richard Baines (Supervisor)

Keywords

  • Cryptochrome
  • Drosophila
  • Magnetosensitivity
  • Electrophysiology
  • Magnetogenetics

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