Talk:Gap junction

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)

My thought would be to agree to leave Electrical Synapse as a separate article for now but perhaps be more explicit in that article that it is a gap junction. The electrical synapse may be thought of as a particular type of gap junction doing a particular job in neurons. It may be that the electrical synapse does the same or similar job in other tissues but in the context of neurons it has specific repercussions that have potential behavioural implications. It may be that gap junctions affect every tissue or organ in a specific way and this will probably warrant more articles being formed but hopefully not with a different name for the gap junction each time as it creates confusion. — Preceding unsigned comment added by Tgru001 (talk • contribs) 04:34, 29 October 2011 (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)

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)

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)

Gap Junctions in the Brain

I may be wrong, but I believe there are much more extensive gap junctions in neurons than the article expresses. Rods and Cones (in Cone-cone (except not blue cones), rod-cone, and rod-rod coupling), horizontal cells, amacrine cells and retinal ganglion (Circuit Functions of Gap Junctions in the Mammalian Retina, S C Massey, 2008). According to Purves (Neurosciences, 3rd ed), brain stem neurons, cerebral cortex, thalamus, cerebellum, and other brain regions have gap junctions. According to Fukuda et. al. in Gap junctions among dendrites of cortical GABAergic neurons establish a dense and widespread intercolumnar network. in J. of Neuroscience 2006 Mar 29;26(13):3434-43, cortical chandelier and basket cells, having on average, 60 gap junctions. These are just what I could come up with in a few minutes... I think it makes this statement: 'Few locations have been discovered where there is significant coupling between neurons in the brain.' sound very misleading.

Pete (talk) 00:52, 26 September 2008 (UTC)

Pete, you are not wrong. I have looked at some parts of the rat brain labeled with immunoflourescent antibodies to gap junction proteins and it lit up like a Christmas tree. With most ultrastructure work you need to look in the right place, at the right stage of developement and with the right techniques. I cant think of any cell type that don't have gap junctions if you look hard enough. There may be exceptions such as chondrocytes in bone but even there I am not certain. Sometimes they are between cells whose cell bodies are widely separated with apparently no connection to their neighbour until you focus through 3D. You will than find long, extremily fine projections of the membrane bound cytoplasm reaching out towards the cell's neighbours over relatively large distances, and where they touch their neighbour's projections you can find connexins forming a gap junction. It is not so much that some cells dont have gap junctions, rather some have huge numbers with up to approx 15% of the membrane area covered with junctional plaques with others so few in number or so diffuse in location they are difficult to detect. user:Tgru001 —Preceding undated comment added 06:30, 6 September 2009 (UTC).

etc.

"...mostly small intracellular signaling molecules..." - I removed this statement, since it isn't always true. In neurons, it is mostly ions that diffuse through gap junctions. Also, I rewrote the beginning to be more concise and technically accurate. Fuzzform (talk) 01:56, 29 September 2008 (UTC)

MERGE

Electrical synapses are gap junctions, so please, MERGE those two articles! (Gap junction and Electrical synapse THANKS!(Myrmeleon formicarius (talk) 18:07, 26 January 2009 (UTC)

p.s.

Pete, you are right. Myrmeleon formicarius (talk) 18:10, 26 January 2009 (UTC)

Wrong link

hi! I can't really handle citations in wikipedia, so I report it here: the link to the article "Hexagonal array of subunits..." (reference 9) leads to a completely different one. Here, you find the correct article: http://www.ncbi.nlm.nih.gov/sites/entrez?db=pubmed&cmd=search&term=Hexagonal+array+of+subunits+in+intercellular+junctions+of+the+mouse+heart+and+liver

Could someone please correct this? Thanks. --Milebrega (talk) 10:05, 13 January 2011 (UTC)

Gap junctions not just connexon pairs

Spending some time rewriting to the article to reflect the last couple of decades research around the functions of connexons outside of gap junctions and the presence of non-conexin proteins within gap junctions.