title: Cathepsin L participates in the production of neuropeptide Y in secretory vesicles, demonstrated by protease gene knockout and expression.
abstract: Neuropeptide Y (NPY) functions as a peptide neurotransmitter and as a neuroendocrine hormone. The active NPY peptide is generated in secretory vesicles by proteolytic processing of proNPY. Novel findings from this study show that cathepsin L participates as a key proteolytic enzyme for NPY production in secretory vesicles. Notably, NPY levels in cathepsin L knockout (KO) mice were substantially reduced in brain and adrenal medulla by 80% and 90%, respectively. Participation of cathepsin L in producing NPY predicts their colocalization in secretory vesicles, a primary site of NPY production. Indeed, cathepsin L was colocalized with NPY in brain cortical neurons and in chromaffin cells of adrenal medulla, demonstrated by immunofluorescence confocal microscopy. Immunoelectron microscopy confirmed the localization of cathepsin L with NPY in regulated secretory vesicles of chromaffin cells. Functional studies showed that coexpression of proNPY with cathepsin L in neuroendocrine PC12 cells resulted in increased production of NPY. Furthermore, in vitro processing indicated cathepsin L processing of proNPY at paired basic residues. These findings demonstrate a role for cathepsin L in the production of NPY from its proNPY precursor. These studies illustrate the novel biological role of cathepsin L in the production of NPY, a peptide neurotransmitter, and neuroendocrine hormone.
authors.affiliation: Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La Jolla, CA 92093-0744, USA.
authors.forename: Lydiane
authors.initials: L
authors.lastname: Funkelstein
authors.forename: Thomas
authors.initials: T
authors.lastname: Toneff
authors.forename: Shin-Rong
authors.initials: SR
authors.lastname: Hwang
authors.forename: Thomas
authors.initials: T
authors.lastname: Reinheckel
authors.forename: Christoph
authors.initials: C
authors.lastname: Peters
authors.forename: Vivian
authors.initials: V
authors.lastname: Hook
mesh_terms: D000313:Adrenal Medulla / Q000201:enzymology* / Q000648:ultrastructure; D000595:Amino Acid Sequence / Q000502:physiology; D000818:Animals; D001921:Brain / Q000201:enzymology* / Q000648:ultrastructure; D056668:Cathepsin L; D002403:Cathepsins / Q000235:genetics* / Q000502:physiology; D002478:Cells, Cultured; D019439:Chromaffin Cells / Q000201:enzymology* / Q000648:ultrastructure; D003546:Cysteine Endopeptidases / Q000235:genetics* / Q000502:physiology; D005455:Fluorescent Antibody Technique; D015971:Gene Expression Regulation, Enzymologic / Q000235:genetics; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D018613:Microscopy, Confocal; D016253:Microscopy, Immunoelectron; D009478:Neuropeptide Y / Q000096:biosynthesis* / Q000378:metabolism; D009490:Neurosecretory Systems / Q000201:enzymology / Q000648:ultrastructure; D016716:PC12 Cells; D010447:Peptide Hydrolases / Q000235:genetics / Q000378:metabolism; D051381:Rats; D022142:Secretory Vesicles / Q000201:enzymology* / Q000378:metabolism / Q000648:ultrastructure
chemical_list: D009478:Neuropeptide Y; D002403:Cathepsins; D010447:Peptide Hydrolases; D003546:Cysteine Endopeptidases; D056668:Cathepsin L; C534278:Ctsl protein, mouse; C534280:Ctsl protein, rat