Dreaming of Science

I had that dream again last night. You know the one – well if you are scientist you will. It’s the dream where you are teetering on the edge of making a great discovery, where the final pieces are falling into place, where the puzzle is almost complete and you will soon know THE ANSWER. That’s what it’s all about after all – knowing THE ANSWER.

The plaudits, recognition and (strictly limited) fame are all secondary to finding out THE ANSWER, when you have A QUESTION.

So, I had this dream – bear with me I do know there is nothing duller than listening to other peoples dreams (holiday photos aside), but this one is different. The difference is that this is all true.

A little background here before I get to the rather exciting main picture on this page. In a nutshell some years ago I was looking for extra-junctional glutamate receptors in the cell membrane of a locust muscle. Glutamate is the main muscle neurotransmitter in insects. It’s what the locust releases from the ends of its nerves to tell its muscles to contract. Interestingly electrophysiology had told us that there seemed to be receptors for glutamate at places other than the neuromuscular junction, which if you think about it is a bit weird (to us, to a locust I’m sure it makes sense). I went looking for them using freeze fracture electron microscopy. I found something I did not expect (see main pictures). This is a micrograph of a massive (relatively) collection of membrane proteins. It’s microns long and each one of those particles represents a protein. That’s a lot of proteins.

Something like this should be also surely somehow be visible in thin section? I looked and found an area of membrane with the required dimensions (smaller picture) that was actually corrugated (as can be seen in stereo micrographs of the freeze fracture replicas) and there were projections visible protruding out from the membrane into the extracellular matrix/space – a possible carbohydrate portion of a glycoprotein? In thin section you could clearly see that these structures did not just occur where cells were in opposition – therefore they do not seem to be part of some strange form of cell-to-cell junction.

I went looking in the literature (sometimes six months in the lab can save a whole morning in the library!) and found that similar structures had been reported before in spiders – didn’t know much about spiders! We did know a bit more about crayfish. In fact they were used in electrophysiological glutamate release studies. I got hold of some crayfish (don’t ask) and I found similar structures in their muscle membranes.

So was this the extrajunctional glutamate receptor complex? If so what on earth was it doing and why was it so huge? Well we knew one more thing about these receptor complexes. If the nerve supply to the muscles was cut (denervation) then after a time the extrajunctional muscle membrane became more sensitive to glutamate. So I denervated a whole bunch of locusts (just the one muscle, that’s tricky) and kept them going for the required time for denervation supersensitivity to set in?

With me so far? Good.

Now I was excited. Would I see loads more of these amazing complexes just appearing?

No.

What I did see was these apparently large junctions breaking up and smaller patches of complex spreading out over the rest of the membrane. Wow!

So was this game set and match for extrajunctional glutamate receptor identification?

In which case why was this complex so large? Far larger than the actual neuromuscular junctional receptor complexes. Why were these complexes preferentially associated with mitochondria? A peer review referee pointed that out! (should have seen it myself). Why were there hundreds and hundreds of proteins and what were they doing in insects, arachnids and crayfish that didn’t seem to be needed to be doing in mammals?

And then I realised! The answer was painfully obvious when the pieces fell into place. Of course, they were …

And then I woke up. Just on the cusp of working out what it was all about … maybe.

That’s what happens when you are a scientist, you see. That is what science is all about. Your brain just doesn’t let go! Won’t let go! It still bugs me.

So any ideas out there? I’m asking, pretty please. As Roy Neary said: “Dammit! This means something. This is important.”