NBME 21 Dilated rough endoplasmic reticulum (NBME Answers)

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submitted by ∗sklawpirt(34)

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I think the idea here is simply that one should think about where vesicles are coming from on their way to the golgi complex.

"Two steps forward and one step back." Specfically the question may be referring to a rare craniofacial disorder. an awarenesss of that disease is not necessary. What is necessary is understanding the origin from where vesicles are traficked to the Golgi apparatus.

COPI protein is needed to coat vescles from the RER to send to golgi. Thus, with a mutation in that protein, the packaged proteins that should bleb off and be sent to the golgi, instead accumulate in the RER and dilate it. Thus the answer.

https://www.cell.com/ajhg/pdf/S0002-9297(16)30214-2.pdf

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hayayah pg. 47 on FA got the good visuals! +6

notadoctor COPII* proteins are needed to coat vesicles from the RER to Golgi. "Two(COPII) steps forward; one(COPI) step back." Anterograde goes RER -> Golgi -> Lysosomes/Secretory Vesicles -> Plasma membrane +27

titanesxvi why not small lysosomes? +5

varunmehru and I thought large lysosomes due to lack of enzymes to degrade +1

samsam3711 The size of the lysosome is not affected by the presence or absence of protein, but its function is compromised (eg. protein is getting stuck in the RER) +2

fattyacid I hope this helps to whomever was lost like me Null mutation: A mutation (a change) in a gene that leads to its not being transcribed into RNA and/or translated into a functional protein product. For example, a null mutation in a gene that usually encodes a specific enzyme leads to the production of a nonfunctional enzyme or no enzyme at all. +3

pingra I think you made a typo: COPII (RER -> cis-Golgi); COPI (trans-golgi -> cis-golgi and cis-golgi -> RER), clathrin (endocytosis and trans-golgi -> lysosome) +2

kevin So my thought process was if there is no COP signal then instead of going to Golgi it would be sent astray into cytoplasm, akin to how in I-cell Dx the enzymes get sent out of the cell since there is no trafficking signal (therefore I presumed large lysosome due to eating the aggregated protein). Are we saying without COP or Clathrin that the vesicle will simply stay put where it is? If I can get a reply before my exam (2 weeks) that'd be much appreciated +2