The Rab35 molecule is the trafficking switch for the fast-track or high-priority recycling pathway signaling the quick return of cargo to the cell surface membrane. It is known that Rab35 exists in two forms, 'on' (GTP- bound) or off (GDP- bound). When Rab35 is turned 'on', it allows the cargo to go back up to the cell surface. What Dr. McPherson and Dr. Ritter and colleagues have discovered is the switch that turns Rab35 on.
"In this study we identified that a particular region of the vesicle-bound protein connecden, , called the DENN domain, is the 'finger' that flips the switch," says Dr. Ritter. "The DENN domain connects with the Rab35 molecule and through enzymatic activity converts Rab35 from the inactive to the active form, in essence, turning on the switch."
DENN domains are found in multiple protein products encoded by 16 human genes. Mutations in the DENN domain cause humans diseases such as sterility and Charcot-Marie-Tooth neuropathy, yet until now the function of this common module has been unknown. The DENN domain is evolutionarily ancient and bioinformatics studies suggest that it is present in all eukaryotic, or multi-compartmental cells, indicating that the DENN domain has mediated crucial functions throughout evolution.
"If the finger or the switch itself is mutated or missing, cargo can't recycle, which has dire consequences," adds Dr. McPherson. "For example a very important cargo transported by this specific fast track recycling pathway, controlled by Rab35 is the MHC class I receptor involved in the immune system response. If a cell becomes infected by a virus, the MHC receptor is loaded with fragments of the virus that have infected the inside of a
|Contact: Anita Kar|