Now we open the sedate, learned pages of Nature Methods, a fine journal that specializes in new techniques in molecular and chemical biology. In the August issue, the correspondence section features. . .well, a testy response to a paper that appeared last year in Nature Methods.
“Experimental challenge to a ‘rigorous’ BRET analysis of GPCR oligimerization” is the title. If you don’t know the acronyms, never mind – journals like this have acronyms like leopards have spots. The people doing the complaining, Ali Salahpour and Bernard Masri of Duke, are taking issue with a paper from Oxford by John James, Simon Davis, and co-workers. The original paper described a bioluminescence energy transfer (BRET) method to see if G-protein coupled receptors (GPCRs) were associating with each other on cell surfaces. (GPCRs are hugely important signaling systems and drug targets – think serotonin, dopamine, opiates, adrenaline – and it’s become clear in recent years that they can possibly hook up in various unsuspected combinations on the surfaces of cells in vivo).
Salahpour and Masri take strong exception to the Oxford paper’s self-characterization:
“Although the development of new approaches for BRET analysis is commendable, part of the authors’ methodological approach falls short of being ‘rigorous’. . .Some of the pitfalls of their type-1 and type-2 experiments have already been discussed elsewhere (footnote to another complaint about the same work, which also appeared earlier this year in the same journal - DBL). Here we focus on the type-2 experiments and report experimental data to refute some of the results and conclusions presented by James et al.”
That’s about an 8 out of 10 on the scale of nasty scientific language, translating as “You mean well but are lamentably incompetent.” The only way to ratchet things up further is to accuse someone of bad faith or fraud. I won’t go into the technical details of Salahpour and Masri’s complaints; they have to do with the mechanism of BRET, the effect on it of how much GPCR protein is expressed in the cells being studied, and the way James et al. interpreted their results versus standards. The language of these complaints, though, is openly exasperated, full of wording like “unfortunately”, “It seems unlikely”, “we can assume, at best” “(does) not permit rigorous conclusions to be drawn”, “might be erroneous”, “inappropriate and a misinterpretation”, “This could explain why”, “careful examination also (raises) some concerns”, and so on. After the bandilleros and picadors have done their work in the preceding paragraphs, the communication finishes up with another flash of the sword:
In summary, we agree with James and colleagues that type-2 experiments are useful and informative. . .Unfortunately, the experimental design proposed in James et al. to perform type-2 experiments seems incorrect and cannot be interpreted. . .”
James and Davis don’t take this with a smile, naturally. The journal gave them a space to reply to the criticisms, as is standard practice, and as they did for the earlier criticism. (At least the editors know that people are reading the papers they accept. . .) They take on many of the Salahpour/Masri points, claiming that their refutations were done under completely inappropriate conditions, among other things. And they finish up with a flourish, too:
"As we have emphasized, we were not the first to attempt quantitative analysis of BRET data. Previously, however, resonance energy transfer theory was misinterpreted (for example, ref. 4) or applied incorrectly (for example, ref. 5). (Note - reference 4 is to a paper by the first people to question their paper earlier this year, and reference 5 is to the work of Salahpour himself, a nice touch - DBL). The only truly novel aspect of our experiments is that we verified our particular implementation of the theory by analyzing a set of very well-characterized. . .control proteins. (Note - "as opposed to you people" - DBL). . . .In this context, the technical concerns of Salahpour and Masri do not seem relevant."
It's probably safe to say that the air has not yet been cleared. I'm not enough of a BRET hand to say who's right here, but it looks like we're all going to have some more chances to make up our minds (and to appreciate the invective along the way).