Talk:Gap junction

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[edit] Merge from electrical synapse

The common term for "electrical synapse" is gap junction. Unfortunately we have an article for each of these terms. Let's merge Electrical synapse into this article, shall we? --David Iberri (talk) 12:51, 31 May 2006 (UTC)

An ephapse is an electrical synapse, normal or pathological. WP has no reference to it, yet it is a commonly used term in explaining various nerve symptoms and diseases. Definitely, when used in that sense, not the same as a gap junction. I suggest an article on ephapse and ephaptic transmission - in the animal nervous system - and am collecting references for that. Are there any authorities that say that electrical synapses and gap junctions are identical? I've never come across any writing that the gap junctions in plants functionally have any resemblance to the ephapse in the human nerve. --198.54.202.254 17:09, 1 July 2006 (UTC) Oops, Forgot to sign in --Seejyb 17:14, 1 July 2006 (UTC)

Isn't an ephapse just a point of contact between adjacent axons that, due to electrical field effects, results in membrane cross-excitation and ectopic action potentials? If they're just points of contact, and aren't anchored by connexons or any of the structural complexes that stabilize chemical synapses, then I believe "synapse" (to clasp) would be a misnomer. In fact, a quick PubMed search reveals that some authors prefer to call it an "artificial synapse" (PMID 168941) or "false synapse" (PMID 707992), probably for this very reason. Ephapses certainly deserve an article, but we shouldn't classify them as true synapses, IMHO.

Regarding the merge: I'm unable to find a reference that says gap junctions and electrical synapses are identical, so I retract the merge proposal. I wish I hadn't made that silly suggestion in the first place. ;-) Gap junctions certainly do more than just couple electrical activity between cells. For example, their pore size allows them to couple cells chemically (eg, they can transmit IP₃, cAMP, and other small signaling molecules). As for gap junctions in plants (presumably you're speaking of plasmodesmata?) and ephapses, I'm not aware of any functional similarities other than electrical coupling.

I propose we

1. create Ephapse (but not Ephaptic transmission -- too much overlap);
2. leave Gap junction, Plasmodesmata, and Electrical synapse as separate articles; and
3. note on Electrical synapse that while ephapses are capable of electrically coupling cells, they are not true synapses.

Thoughts? --David Iberri (talk) 23:49, 1 July 2006 (UTC)

A remark on the following part: Connexin proteins expressed in neurons include: mCX26 mCX43 mCX36 mCX56.6 mCX57 mCX45 PX1 PX2

The PX1 and PX2 proteins are NOT members of the connexin family, they are pannexins. However, as it appears from recent literature, pannexin channels between cells do cause electrical coupling between cells. The genes encoding for pannexin proteins are different from the genes encoding connexins.

Agreed- Pannexins are NOT members of the Connexin family. They have no sequence homology at all. In fact, there is no evidence that pannexins actually form gap junctions in vivo. They can form junctions after exogenous over-expression, particularly in paired Xenopus oocytes, but this may not be representative of their true function. Besides, they are glycosylated in vivo, making them even less likely to form gap junctions. Until there is evidence that they form gap junctions in vivo, their inclusion is misleading. Wrs1971 15:58, 3 April 2007 (UTC)

[edit] Hypothetical innexin family?

How can the innexin family be hypothetical? Does it mean that the innexins themselves are established, and there's a hypothesis that they form a family? A reword would be helpful. --Reuben 21:55, 11 September 2007 (UTC)

[edit] Misspelling?

In the text it currently states as follows "At gap junctions, the intercellular space narrows from 25nm to 3nm..."

Doesn't make sense, should it be 2.5 to 3 nm? Tobias Larsson (talk) 13:52, 9 March 2008 (UTC)