Long lived protein demixing in flagella

Cells create different internal compartments by diffusional uncoupling of one part of the cells from another. This helps cells to maintain different protein concentrations in different parts of the cell, which is used for creating compartments with specialized functions. Well known examples are provided by membrane bound organelles such as the nucleus and mitochondria, or phase separated structures such as the nucleolus. In this talk I will discuss another mechanism for creating a diffusionally decoupled region within the cell, which is achieved at the tips of flagella by motor-driven transport of molecules toward the tip. An example of this is provide by the localization of kinesin-13 proteins to the tips of flagella in Giardia [1]. In this talk, I describe a simple physical model of combined directed transport and diffusion that leads to diffusional uncoupling of the flagellar tip from the cell body over time scales that are exponential in the length of the flagellum. I comment on the theoretical possibility of this mechanism providing the graded staircase geometry of stereocilia in hair cells of the inner ear.

 

References:

[1]   S. G. McInally, J. Kondev, and S. C. Dawson, “Length-dependent disassembly maintains four different flagellar lengths in Giardia,” eLife, vol. 8, p. e48694, Dec. 2019, doi: 10.7554/eLife.48694.