Message on the web: mRNA and ER co-trafficking

In eukaryotes, mRNAs encoding secreted and integral membrane proteins are targeted to the endoplasmic reticulum (ER) to facilitate translation and protein translocation into the ER lumen. However, mRNAs encoding cytosolic proteins also associate with ER membranes in yeast, plants and animal cells. mRNAs encoding both cytosolic and secreted proteins have been observed in association with the cortical ER (cER) network, which consists of interconnected tubular and sheet-like structures that extend to the plasma membrane and to sites of polarized growth. This physical association enables cytoskeleton-mediated co-trafficking and anchoring of cER-mRNA, which might regulate protein synthesis in areas of new growth (i.e. during cell division in yeast), or enable confined spatial responses to environmental stimuli (i.e. during synaptic remodeling or in cases of neuronal injury).