Cell-cycle-dependent trafficking in the endocytic pathway

Abstract

In the endocytic pathway, many components are degraded. This is essential for cells in many ways, like uptake of nutrients, defense against pathogens, receptor downregulation, and antigen processing. In interphase, the endocytic pathway is highly dynamic and receives components both from the plasma membrane and from the trans-Golgi network. In mitosis, many cellular processes are downregulated. Secretion is arrested in mitosis, and both the Endoplasmatic Reticulum and the Golgi complex fragments. Little is known about the organelles in the endocytic pathway in mitosis, the endosomes and lysosomes. During this project we have studied endosomes and lysosomes both in interphase and mitosis. We have specially focused on the early endosomal tethering factor, EEA1, which is an important molecule that brings early endosomes in close proximity to facilitate SNARE assembly with a following fusion. EEA1 is a molecule that cycles between early endosomes and cytosol. This on/off cycling we have found to be rapid and highly variable, and these changes in on/off cycling we suggest make EEA1 a sensitive regulator for tethering prior to fusion.