Question

Which of the following about the multi-vesicular endosomal pathway are TRUE

ESCRT complexes create multiple vesicles in the lumen of the late endosome

Proteins targeted for degradation are retained outside the vesicles in the endosomal lumen

Proteins targeted for degradation are placed inside vesicles in the endosomal lumen

HIV utilizes the ESCRT complexes to transfer itself into the lysosome for degardation

Answer 1

Solution: The True statement is, ESCRT complexes create multiple vesicles in the lumen of the late endosome. Also the statement Proteins targeted for degradation are retained outside the vesicles in the endosomal lumen, can be considered as partialy correct.

During multivesicular endosome formation, small vesicles are pinched off into to the lumen of late endosome. membrane of those vesicle carries proteis which are supposed to degrade with in the acidic environment of lysosome, when the late endosome fuses with lysosome. The formation of multivesicular bodies are mediates by a protein complex called as ESCRT complex. ESCRT in association with other factors such as mono-ubiquitinated Hrs protein and Vps4(ATPase protein) helps the pinching of small endosome vesicles into the endosome lumen.

The proteins which are directed for degradation in the lysosomal lumen are carreid by these multivesicular bodies. The multivesicular bodies carry those proteins on their membrane and when the late endosome fuses with lysosome, these small endosomal vesicles are brought inside the acidic environment of lumen so that lysosomal enzymes can degrade them.