Bradley, Alexander

Alexander is in the Biochemistry, Molecular, and Structural Biology graduate program in the laboratory of Dr. Margot Quinlan, and joined the CMB Training Program in 2015.  He received a B.S. degree in 2014 from Arizona State University.

Mentor: Dr. Margot Quinlan

Research project:

Actin is an abundant protein found in nearly every eukaryotic cell. It is a determinant of cell structure/morphology and plays a role in motility, division, and muscle contraction. Actin’s ability to assemble from a globular form into protein filaments, many microns long, is central to these roles. Spir and Capu have been established as essential regulators of actin dynamics. The import of their interaction is evident by the profound loss in fertility observed in Drosophila melanogaster (the fruit fly – our model organism) when regions necessary for their interaction with one another are mutated. Spir and Capu were implicated in the proper temporal control of ooplasmic streaming – a fascinating and still incompletely understood process by which oocytes mix their contents like a washing machine. Spir and Capu are essential for the properly timed construction of an actin mesh, which inhibits premature cytoplasmic fast-streaming. Premature streaming results in reduced fly fertility. Study of the synergy between Spir and Capu provides insight into the interplay between similar proteins in human and other mammalian cells. I seek to clarify the in vivo co-localization behavior of Spir/Capu and articulate their mechanism, while identifying potential, novel regulators.

I am developing a FRET pair of Spir and Capu for measurement in vivo, to determine their spatiotemporal interaction; that is, to visualize when and where they are found together, in oocytes. Perturbations in this FRET system will allow for identification of novel Spir/Capu interacting proteins. In addition, I have used tiny beads, bearing various tags, to non-covalently anchor either Spir or Capu to a structure resembling vesicles found in the cell. I then add other known components of the system and visualize the dynamic behavior of actin, relative to the beads and what is bound to them. The controlled geometry of beads affords the possibility of a somewhat true-to-life reconstitution of the actin mesh assembly system, in vitro, which may then be utilized to investigate the components of this elaborate coordination in greater complexity.