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Biosynthesis of intestinal microvillar proteins. Surface expression of aminopeptidase N is not affected by
Abstract:
The effect of chloroquine on the biosynthesis of pig intestinal aminopeptidase N (EC 3.4.11.2) was studied by labelling with [35S]methionine in organ cultured mucosal explants. The lysosomotropic agent did not alter the molecular size of either the transient or the mature form of the enzyme and did not markedly influence the relative intracellular distribution of the two forms. The microvillar expression of aminopeptidase N during labelling periods of 80-120 min was found to be unaffected by chloroquine. Together these data indicate that pH neutralization of the acidic compartments of the cell bears no consequence on the intracellular transport of the newly synthesized microvillar enzyme. This suggests that the acidic compartments are not involved in the post-Golgi transport and that this, in turn, probably occurs via a constitutive rather than a regulated pathway.
Insights
Chloroquine does not affect the synthesis or transport of pig intestinal aminopeptidase N. This suggests acidic compartments are not vital for post-Golgi transport of this microvillar enzyme.
Area of Science:
- Biochemistry
- Cell Biology
- Enzymology
Background:
- Aminopeptidase N is a key microvillar enzyme.
- Lysosomotropic agents like chloroquine affect intracellular pH.
- Understanding enzyme transport pathways is crucial.
Purpose of the Study:
- To investigate the effect of chloroquine on aminopeptidase N biosynthesis.
- To determine the role of acidic compartments in enzyme transport.
Main Methods:
- Organ culture of pig intestinal mucosal explants.
- Biosynthetic labeling with [35S]methionine.
- Analysis of enzyme molecular size and intracellular distribution.
Main Results:
- Chloroquine did not alter the molecular size of transient or mature aminopeptidase N.
- Intracellular distribution of enzyme forms remained unchanged.
- Microvillar expression of aminopeptidase N was unaffected by chloroquine.
Conclusions:
- Acidic compartments are not involved in the post-Golgi transport of newly synthesized aminopeptidase N.
- Intracellular transport of this microvillar enzyme likely occurs via a constitutive pathway.