Small GTPASE ARL3 Regulates Flagellar Motility in Chlamydomonas reinhardatii

Abstract

Movement of proteins and cargo from the cell body to the flagellar tip is carried out by the intraflagellar transport system (IFT). IFT is composed of multiple protein subunits that are responsible for the building and maintenance of the flagella. ADP- Ribosylaition Factor Like-3(ARL3) is an evolutionarily conserved protein found in all ciliated organisms that is hypothesized to play a role in IFT. ARL3 is a small GTPase that interacts with ciliary proteins as an allosteric regulator, effector, and localizer of proteins associated with retinal photoreceptor issues, retinisis pigmentosa, and poly cystic kidney disease respectively. Mutants with the ARL3 gene disrupted in Chlamydomonas reinhardtii display impaired swimming ability and quick deflagelleation. In an attempt to rescue the mutants, three independent point mutations gave rise to the ARL3 protein actively GTP bound, inactively GDP bound, and in a wildtype interchanging form. Swim speed tests and flagellation rate of wild type insertional mutants showed statistically insignificant difference from naturally occurring wild type in their ability to swim and flagellate. While the active and inactive forms show a significant difference in flagellation rate and swimming ability. Results support our hypothesis of Arl3’s localization along the flagellar membrane and within the basal body of Chlamydomonas reinhardtii. The goal of this project is to reestablish proper ciliary function in these ARL3 disputed mutants via transformation of a wildtype plasmid. If successful, similar methods could be implemented to resolve impaired ARL3 found in polycystic kidney disease and photoreceptor malformations.