All hail the mighty MitoPits!
Cansu Küey’s PhD work was published this week in eLife. Together with Méghane, Gabrielle and Miguel, she showed that clathrin-coated pits can be made to form on intracellular membranes. This phenomenon allowed us to redefine two key concepts in clathrin-coated vesicle formation. First, a scission molecule is not needed to pinch off vesicles inside the cell. Second, that most of the other proteins found in regular clathrin coats are not essential for vesicle formation.
Cansu worked in the Royle lab as a SynBio PhD student from 2018 to 2021 and also happened to graduate this week!
The formation of a clathrin-coated vesicle is a major membrane remodeling process that is crucial for membrane traffic in cells. Besides clathrin, these vesicles contain at least 100 different proteins although it is unclear how many are essential for the formation of the vesicle. Here, we show that intracellular clathrin-coated formation can be induced in living cells using minimal machinery and that it can be achieved on various membranes, including the mitochondrial outer membrane. Chemical heterodimerization was used to inducibly attach a clathrin-binding fragment 'hook' to an 'anchor' protein targeted to a specific membrane. Endogenous clathrin assembled to form coated pits on the mitochondria, termed MitoPits, within seconds of induction. MitoPits are double-membraned invaginations that form preferentially on high curvature regions of the mitochondrion. Upon induction, all stages of CCV formation - initiation, invagination, and even fission - were faithfully reconstituted. We found no evidence for the functional involvement of accessory proteins in this process. In addition, fission of MitoPit-derived vesicles was independent of known scission factors including dynamins and dynamin-related protein 1 (Drp1), suggesting that the clathrin cage generates sufficient force to bud intracellular vesicles. Our results suggest that, following its recruitment, clathrin is sufficient for intracellular clathrin-coated vesicle formation.
Read the paper here.