It is natural to hypothesize that similar processes in the cell may use the same proteins to do the job. So, it is very satisfying to the scientists who identify these proteins and add another piece to the cellular puzzle.
Lysosomes are organelles that break down the cell’s waste material, which reach lysosomes from a few pathways. Endocytosis is the uptake of material from the outside surface of the cell, and this material gets shuttled through different vesicles, some of which lead to lysosomes. Authophagy is the process in which a cell’s own components are transported to lysosomes in double-membrane vesicles for degradation. A recent paper identifies the mechanism of two proteins, called Rubicon and PLEKHM1, that play a role in both endocytosis and authophagy through their interaction with Rab7, a well-known small GTPase that is found on both late endosomes and lysosomes. Images show endosomes (left column, green in merged) and PLEKHM1 (middle column, purple in merged) with different Rab7 mutants. In cells with wild-type Rab7 or a Rab7 QL mutant, PLEKHM1 was localized to endosomes (white in merged indicates colocalization). In the dominant-negative Rab7 TN mutant, PLEKHM1 could not localize to endosomes.Tabata, K., Matsunaga, K., Sakane, A., Sasaki, T., Noda, T., & Yoshimori, T. (2010). Rubicon and PLEKHM1 Negatively Regulate the Endocytic/Autophagic Pathway via a Novel Rab7-binding Domain Molecular Biology of the Cell, 21 (23), 4162-4172 DOI: 10.1091/mbc.E10-06-0495