immunization-alpacas-lama-pacos-with-protein-antigens-production

Immunization of Alpacas (<em>Lama pacos</em>) with Protein Antigens and Production of Antigen-specific Single Domain Antibodies

In this manuscript, a method for the immunization of alpaca and the use of molecular biology methods to produce antigen-specific single domain antibodies ...

University of Kentucky

Neprilysin is a zinc metalloendopeptidase with relatively broad substrate specificity. The enzyme is localized to the plasma membrane of cells where it can function to degrade extracellular peptides. Structural studies show that neprilysin preferentially cleaves peptides on the amino side of hydrophobic amino acids. Neprilysin has been implicated in the catabolism of amyloid beta peptides in the brain and as such has received considerable attention, particularly as a therapeutic target for Alzheimer's disease. An inverse relationship between neprilysin levels and amyloid beta peptide levels and between neprilysin levels and amyloid plaque formation has been observed in human brain. Neprilysin levels decline with aging in the temporal and frontal cortex possibly contributing to higher amyloid beta peptide levels. A number of studies have shown that increasing neprilysin levels in the brain leads to a decrease in brain amyloid beta peptide levels. Most recently a potential relationship between amyloid beta peptide synthesis from the amyloid precursor protein and neprilysin activity has been proposed.

Neprilysin and amyloid beta peptide degradation.

Insulin-degrading enzyme (IDE) hydrolyzes bioactive peptides, including insulin, amylin, and the amyloid β peptides. Polyanions activate IDE toward some substrates, yet an endogenous polyanion activator has not yet been identified. Here we report that inositol phosphates (InsPs) and phosphatdidylinositol phosphates (PtdInsPs) serve as activators of IDE. InsPs and PtdInsPs interact with the polyanion-binding site located on an inner chamber wall of the enzyme. InsPs activate IDE by up to ∼95-fold, affecting primarily  The extent of activation and binding affinity correlate with the number of phosphate groups on the inositol ring, with phosphate positional effects observed. IDE binds PtdInsPs from solution, immobilized on membranes, or presented in liposomes. Interaction with PtdInsPs, likely PtdIns(3)P, plays a role in localizing IDE to endosomes, where the enzyme reportedly encounters physiological substrates. Thus, InsPs and PtdInsPs can serve as endogenous modulators of IDE activity, as well as regulators of its intracellular spatial distribution.

Inositol phosphates and phosphoinositides activate insulin-degrading enzyme, while phosphoinositides also mediate binding to endosomes.

Insulin-degrading enzyme (IDE) functions in the catabolism of bioactive peptides. Established roles include degrading insulin and the amyloid beta peptide (Aβ), linking it to diabetes and Alzheimer's disease. IDE is primarily located in the cytosol, and a longstanding question is how it gains access to its peptide substrates. Reports suggest that IDE secreted by an unconventional pathway participates in extracellular hydrolysis of insulin and Aβ. We find that IDE release from cultured HEK-293 or BV-2 cells represents only ~1% of total cellular IDE, far less than has been reported previously. Importantly, lactate dehydrogenase (LDH) and other cytosolic enzymes are released at the same relative level, indicating that extracellular IDE results from a loss of cell integrity, not secretion. Lovastatin increases IDE release from BV-2 cells as reported, but this release is mirrored by LDH release. Cell viability assays indicate lovastatin causes a loss of cell integrity, explaining its effect on IDE release. IDE is present in an exosome-enriched fraction from BV-2 cell conditioned media, however it represents only ~0.01% of the total cellular enzyme and is unlikely to be a significant source of IDE. These results call into question the secretion of IDE and its importance in extracellular peptide degradation.

Article	Year
Neprilysin and amyloid beta peptide degradation. Current Alzheimer research\| PubMed ID: 18393807	2008
Inositol phosphates and phosphoinositides activate insulin-degrading enzyme, while phosphoinositides also mediate binding to endosomes. Proceedings of the National Academy of Sciences of the United States of America\| PubMed ID: 28325868	2017
Insulin-degrading enzyme is not secreted from cultured cells. Scientific reports\| PubMed ID: 29402917	2018

Louis B. Hersh

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