The gap junction only permits small molecules (less than 1 KD) to shuttle from one cell to another. I remember the GFP MW is about 30kd. I think it’s too big for GFP to pass through the gap junction.

I agree with Krzysztof. Such "leakage" occurs only in few cell types, e.g. in cardiomyocytes.

Best

Darius

No, GFP does not cross gap junction channels.

The gap junction only permits small molecules (less than 1 KD) to shuttle from one cell to another. I remember the GFP MW is about 30kd. I think it’s too big for GFP to pass through the gap junction.

Gap junction channels do not allow for the transfer of any protein, as far as I know. However, GFPs can be transfer between cells expressing connexins (or innexins if your model of development is in invertebrates) in a non-channel dependent manner. The first is through tunneling nanotubes that depend on connexin expression but the transfer of cargo between cells is not through the gap junction channels. Second is the internalization of annular gap junctions where one of the cell pair invaginates the entire gap junction plaque, including membrane and part of the cytoplasm of the other cell. A third (less likely) possible explanation of GFP transfer is through the formation of cytoplasmic bridges. In all cases, the transfer of GFPs between cells should be very low, so using its expression as a cell fate marker is OK.

Here goes a reference for each pathway in case you need them.

I agree with Nicolas: GFP alone can not travel between cells.

For GFP, it's not a case. Too big to cross. But who knows it for sure. A recent Nat Med paper demonstrated that GJ-mediated communication between cells endorsed mitochondria transfer between bone-marrow strom cells and ATII cells. Is GFP secreted somehow and engulfed by another cell depending on GJs communication?

indeed, GFP, its is inposible to transfer between cells via gap juction, due to it's large molecular weight

Hi Aadeshkumar

Just another thing to think about. Although GFP cannot transfer between cells via gap junctions, it can via apoptosis of a GFP positive cell and uptake of GFP-containing vesicles by neighbouring cells. This is cell-type dependent however, and requires apoptosis (not necrosis) to occur.

Al

I agree with Nicolas, moreover in overexpression assays we detect a high proteolysis of GFP, it is important to control this issue. GFP is fantastic, but have problems no minor

Dear Aadeshkumar Shendge, dear other posters,

unfortunately the questioner did not say anything about the cells he is using (going to use) for his study.

It is interesting that most commenters think about an impossibility of permeation/penetration of GFP through a gap junction due to the large molecular weight (27-31 kDa). On the other hand, Nicolas Palacios-Prado has indicated thankfully the possibility that GFP can / has been reported to get through gap junctions (?), especially if the reporter protein is bound to connexins which are a major constituent of special cellular junctions – not only in skin (there are at least some 10-20 very interesting papers related to this).

Concerning the barrier function for “high molecular weight” molecules I found links (eg. also: http://www.wisegeek.com/what-are-gap-junctions.htm, http://www.biologyreference.com/Ce-Co/Cell-Junctions.html ), stating that small molecules of 1,500 daltons or less can pass through the channel of each gap junction.

So IMHO, if, for example, Aquorea GFP is a protein of 238 amino acids with a molecular weight of 27 or 30 kDa it is a “wonder” that GFP can be found passing gap junctions via connexins (or are the connexons here serving as a kind of “transponders”)…. “Different connexin proteins, in particular when expressed in the same cell type, may form gap junctional channels of different permeability ( cf. jcb.rupress.org/content/129/3/805.full.pdf : Lucifer yellow can pass, MW 0.46 kD)".

An interesting question, not only for/in basic research (cf. eg. http://ajpcell.physiology.org/content/295/4/C966.full :

[2008]).

Unfortunately I was not able to find (a) reference(s) in which ultimatively was shown an active/passive transport of GFP via a “gap junction”. So it might depend on further specific studies to be able to definitively answer this question. I should be glad to read about such references found by anybody of the honest posters in this thread. Best wishes and regards,

Wolfgang MUSS, Salzburg, Austria

I should clarify one point from my previous post: FPs can be transfer between cells expressing connexins, but the transfer is not through the gap junction channel lumen. As for which molecules can be transfer through gap junction channels, molecular weight cutoffs alone are not very useful. Gap junction channels formed by different Cxs show a remarkable variation in permeability (http://www.ncbi.nlm.nih.gov/pubmed/18378797) , and for each Cx, permeability for a given molecule depends on molecular weight, net charge and 3D shape of the molecule. For example, oligonucleotides with molecular weight up to ~4 kDa and diameter of 1 nm have been reported to cross gap junction channels formed by Cx43, but not by Cx26 or Cx32 (http://www.ncbi.nlm.nih.gov/pubmed/16037090). Another example is the transfer of linear small peptides with molecular weight of 1.8 kDa through Cx43 gap junction channels (http://www.ncbi.nlm.nih.gov/pubmed/15744304).

Dear Nicolas, thank you for your additional post,

Wolfgang