Scientists have known about the endoplasmic reticulum for nearly seven decades: It's a protein-synthesizing object squished inside our cells next to nucleoli and mitochondria and all the other fun organelles.
But what they didn't realize up until now is that the ER has a shape very similar to one of the world's most mundane structures: the spiral-ramped parking garage. That's right – if you were a member of that "history-making" team that piloted a submarine into a human body in 1966, you conceivably could've spent hours wandering around the reticulum, trying to remember where you parked the dang thing.
The startling discovery of the ER's "helicoid" was made by Mark Terasaki of the University of Connecticut Health Center and researchers from Columbia, Harvard, Tel Aviv University and elsewhere; the journal Cell published the news in a July 18 paper titled, "Stacked Endoplasmic Reticulum Sheets Are Connected by Helicoidal Membrane Motifs." What's behind the corkscrew in our cells? Well, the ER is dotted with molecules called ribosomes that are in the business of making proteins. One of the most efficient shapes for sheltering tons of ribosomes happens to be the spiral, because it maximizes surface area in a small amount of space. And thus it "resembles a parking garage," according to the study's abstract, "in which the different levels are connected by helicoidal ramps."
Here's the revolutionary new image of it:
To pound on the parking-lot similarity some more, if a cell wants to increase its protein production, it adds layers to the reticulum, kind of like how a developer would bulk up a garage. Science Codex goes into the explanation for that:
When a cell needs to secrete more proteins, it can reduce the distances between sheets to pack even more membrane into the same space. Think of it as a parking garage that can add more levels as it gets full. "The theory explains that this structure is seen in nature because it maximizes the cell's ability to make a large number of proteins while minimizing the energetic cost to the cell," Rapoport says.
Excellent work, guys. Now please get cracking on the next problem: Is it true that the Golgi apparatus really looks like a waste-transfer station?
Top image courtesy the journal Cell