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I am considering the transport of protein from ER to Golgi, and have read that this involves the COPII protein coat. I have also read that this is a form of anterograde transport, and elsewhere that kinesins are responsible for anterograde transport as they move from the negative to positive (outside) poles of the microtubules.

Thus it seemed to me that the kjnesins carry the COPII vesicles carrying proteins from ER to Golgi.

However a Google search of the terms 'kinesins' and 'COPII' together did not seem to yield anything about kinesins carrying COPII.

On the other hand in this article it links COPII with dynsctjn, which I have not heard of before.

Does someone know the link between COPI and COPII transport, and/or retrograde and anterograde transport, with the microtubule motor proteins kinesin and dynein? Where do dynectins come into this? Do they bind the vesicle to the dynein or are they a different type of motor protein? If it is the first case, then why is this transport termed anterograde if it does not use kinesins? Are the terms anterograde and retrograde not directly related to kinesin/dyneins use?

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  • $\begingroup$ The link in your question doesn't point to any article. $\endgroup$ – canadianer Mar 27 '17 at 3:26
  • $\begingroup$ @canadianer Apologies . It seems I did not copy the end of the url link. I have corrected this now. Thank you for letting me know@ $\endgroup$ – 21joanna12 Mar 27 '17 at 9:03
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Interesting question. The term anterograde refers to movement in the forward direction. In the context of vesicular trafficking, anterograde refers to (1) movement from the site of protein synthesis in the rough endoplasmic reticulum (RER) towards the Golgi and then (2) movement from the Golgi towards the final destination in the cell.

Both processes rely on microtubules for transport. Microtubules are polar and radiate from the microtubule organizing center (MTOC) with their (+) ends directed towards the periphery of the cell:

enter image description here

There are two broad classes of molecular motors that facilitate directed movement along microtubules. Kinesins are generally (+)-end directed motors whereas dyneins are (-)-end directed:

enter image description here

These images should already give you a hint. Your question may have arisen due to the assumption that the ER is centrally located near the MTOC with the Golgi somewhat peripheral. This is incorrect. In reality, the Golgi complex is actively clustered near the MTOC by movement on microtubules. Furthermore, the ER extends along the microtubule network towards the (+)-end periphery. Taken together, it is evident that microtubule (-)-ends are located near the Golgi and transport to it from any part of the cell, including the RER, requires the (-)-end directed motor dynein. Subsequent anterograde transport from the Golgi to a specific destination in the cell, or through the secretory pathway, requires the (+)-end directed motor kinesin. Retrograde transport from the Golgi back to the ER would also use kinesin:

enter image description here


The article cited in the question (which I also reference in this answer), mentions that COPII vesicles are coupled to microtubules via dynactin. Dynactin is a protein complex that is used to both activate and adapt cargo to dynein (ie COPII vesicles are coupled to microtubules via a dynein/dynactin complex):

enter image description here

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    $\begingroup$ Thank you for your reply! Just to make sure I understand correctly, for a secreted protein they would be carried by dynein from the ER to Golgi and then by kinesins from the Golgi to the cell surface membrane? Also, dynactin was entitled in the article as the way COPII bind to the microtubule. What is this third protein? $\endgroup$ – 21joanna12 Mar 27 '17 at 9:06
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    $\begingroup$ @21joanna12 Yeah that sounds right to me. I'll edit my answer shortly to address dynactin. $\endgroup$ – canadianer Mar 27 '17 at 17:53

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