The endoplasmic reticulum (ER) is the largest organelle in a cell and uses tiny molecular motors to change its shape in response to cellular stress. The ER forms membrane contact sites (MCS) with all other organelle types. These MCS rely on microtubule-based transport of ER tubules via molecular motor association with Rab-GTPases (Rabs) to direct accurate and specific cargo transport. Defects in ER MCS have been associated with numerous diseases, including cancer and neurodegeneration. 

Canonically, the ER has been shown to move on microtubules to form MCS by two mechanisms: sliding (association with a molecular motor via a cargo adaptor), and tip attachment complexes (associating with the plus end of a dynamic microtubule). Now, new work by John Salogiannis, PhD, and trainee Allison Langley, published in Molecular Biology of the Cell, finds that the ER can move by a third, novel mechanism, known as “hitchhiking”. ER movement via hitchhiking occurs when ER tubules associate with motile Golgi-derived vesicles marked by Rab6. The authors show that this mechanism of ER movement contributes significantly to overall ER movement, which is critical for maintaining cellular homeostasis.

In the future the authors plan to identify which proteins are key for tethering ER tubules to Rab6 vesicles, to better understand how cellular needs dictate which ER movement mechanism is utilized, and to identify the biological functions of ER hitchhiking.

Learn more about this work and view the incredible videos of ER movement here.