Does Kinesin Play a Role in Cell Membrane Dimpling During Endocytosis?

[SarcasticSimb]

Hello!

So in AP Biology today, we were discussing the multiple ways cells "eat", (exocytosis, phago- and pinocytosis). I asked my teacher if kinesin is used to create the "dimple" on the edge of the cell membrane during endocytosis; my teacher was clearly baffled, and ranted about the difference between phago- and pinocytosis.

Related: does that "dimple" have a name?

Please reply if you know, and if you have any other cellular biology questions, feel free to ask in this thread. Although I'm still in high school, I've read up a LOT on cellular biology (especially the chemistry behind it).

Thank you!
~SarcasticSimb

 

[Ygggdrasil]

In the best studied example of endocytosis, clathrin-mediated endocytosis, the recruitment of a protein called clathrin to the membrane helps to create the "dimple" (the scientific term would be invagination) in the membrane. Clathrin is composed of many copies of two proteins, clathrin light chain and clathrin heavy chain. These proteins assemble into a cage-like structure (looks somewhat like a football/soccer ball). Basically, the energy from the binding of clathrin molecules to each other provides the energy to induce curvature in the membrane and bring it into the cell.

Other proteins are involved, of course. For example, pinching off the membrane to release the clathrin-coated vesicle into the cell requires a protein called dynamin which uses the energy from ATP hydrolysis in order to sever the vesicle from the plasma membrane. After the clathrin-coated vesicle has been pinched off, it can be recruited to motor proteins like kinesin for transport farther into the cell.

In addition to clathrin-mediated endocytosis, other means of endocytosis exist. For example, certain viruses are brought into the cell by processes that are driven by the polymerization of actin, a protein that forms part of the cell's cytoskeleton. Many of these other pathways are not so well studied and are scientists are still trying to learn more about these pathways (including clathrin-mediated endocytosis).

edit:
For more on clathrin-mediated endocytosis, see the following two videos. The first explains the process better, but the second has a very entertaining video showing a nice animation of the process of clathrin-mediated endocytosis:


https://iwasa.hms.harvard.edu/project_pages/endocytosis/endocytosis.html

 

[bobze]

Also to add, clathrin-coated pits (the names scientists call them) don't form de novo for pinocytosis. Their formation is mediated through interactions with adapter proteins (rightly called adaptins) which allow the cytosolic domain of transmembrane receptor proteins (for absorptive, specific ligand mediated endocytosis) to start forming the clathrin coated pit.