I study two protein isoforms of WNT5A that differ from one another by only 18 amino acids post-processing. These isoforms are highly conserved among vertebrates. We see no evidence that these isoforms are functionally distinct from one another. With every assay I do, it looks more and more like the isoforms are completely redundant.
Assuming that these isoforms are functionally redundant, what could possibly be driving them to be so highly conserved?
I would not expect them to be functionally redundant; I guess there may be subtle differences difficult to detect. If that were the case one or the other would have been lost during evolution. In the case they were actually redundant, their conservation could be related to regulatory processes at the transcript level (may be one isoforms mRNA has shortest life or is more/less efficiently tranlsated).
I recommend this reference:
Kelemen, Olga, et al. "Function of alternative splicing." Gene 514.1 (2013): 1-30. One of their conclusions was that changes in function introduced by AS are hard to detect.
Hi Carl,
I've just very quickly checked your protein and the N-term (first 35 residues) seems to have a signaling peptide. Are the 2 isoforms in the same cell compartment? have you checked post-translational modification sites?
Frederico,
I had considered the idea of very nuanced and difficult to detect differences in function at the protein level. It's certainly possible, but it's not an idea I'm too thrilled about given that it's necessarily a dead end. However, the idea that the alternative transcripts differ in stability is testable, and something that I hadn't considered. Thanks!
Filippo,
There's not much of a reason to think that they are differentially modified post-translation, but it's certainly a possibility. Typically Wnt proteins are palmitoylated and glycosylated prior to secretion. Both are required for activity for one of the isoforms. Since the other has been shown to be active, we assume they are similarly modified. We've never directly tested this, however. Both proteins are secreted ligands. Thank you!
I appreciate both of your answers very much - it helps greatly to have a fresh set of ideas.
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