An adhesion GPCR regulates cell adhesion and mating in the closest living relatives of metazoans
This study identifies Cupidon, an adhesion GPCR in the choanoflagellate *Salpingoeca rosetta*, as a dual-function regulator that suppresses cell aggregation under nutrient-rich conditions but promotes gamete fusion during starvation-induced mating, thereby demonstrating that aGPCR-mediated control of cell adhesion predates the origin of metazoans.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of a preprint that has not been peer-reviewed. It is not medical advice. Do not make health decisions based on this content. Read full disclaimer
Imagine the history of life as a massive construction project. Before complex animals (metazoans) could build their multi-cellular cities, the very first "bricks"—single-celled organisms—had to learn how to stick together and talk to one another. Scientists have been looking for the "blueprints" or the "foremen" that made this possible.
In this study, researchers looked at a tiny, single-celled organism called Salpingoeca rosetta. Think of this creature as the "great-great-grandparent" of all animals. It's the closest living relative we have to the very first animals that ever existed. The team was hunting for a specific tool that helps these cells decide when to stick together and when to stay apart.
They found a master switch called Cupidon.
To understand what Cupidon does, imagine it as a smart, dual-mode traffic controller for these cells.
Mode 1: The "Stay Apart" Signal (When Food is Plenty)
When the cells are well-fed and happy, Cupidon acts like a strict security guard. It puts up "Do Not Disturb" signs. Specifically, it stops the cells from clumping together. It does this by blocking a sticky substance (like a biological glue) that usually helps them hold hands. In this mode, Cupidon says, "We have enough food; no need to huddle up."
Mode 2: The "Get Together" Signal (When Food Runs Out)
When the food runs out, the situation changes. The cells go into emergency mode and start preparing to reproduce. They transform into two different types of "gametes" (sex cells):
- Females grow a long, extended "collar" (like a fishing net).
- Males grow a special "fertilopod," which is like a grappling hook or a docking arm.
Here is where Cupidon gets creative. It undergoes a makeover. It gets chopped up by the cell's internal machinery and moves to a new location. Instead of keeping the cells apart, Cupidon rushes to the exact spot where the male's "grapple" meets the female's "net."
At this meeting point, Cupidon acts like a matchmaker and a super-glue. It facilitates the final step: fusing the two cells together to create a new life.
The Big Takeaway
The most exciting part of this discovery is the timeline. Scientists used to think that complex cell-to-cell communication tools (like Cupidon) only evolved after animals appeared. But this paper shows that Cupidon was already working in the ancestors of animals, long before true multicellular life existed.
In short, the "foreman" that taught cells how to stick together and mate was already on the job site before the first animal city was ever built. Cupidon proves that the rules for cell adhesion and mating were written in the ancient past, long before we humans or even simple sponges walked the Earth.
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