Identification of Domain Structures in the Propeptide of Corin Essential for the Processing of Proatrial Natriuretic Peptide

Abstract

Corin is a type II transmembrane serine protease and functions as the proatrial natriuretic peptide (pro-ANP) convertase in the heart. In the extracellular region of corin, there are two frizzled-like cysteine-rich domains, eight low density lipoprotein receptor (LDLR) repeats, a macrophage scavenger receptor-like domain, and a trypsin-like protease domain at the C terminus. To examine the functional importance of the domain structures in the propeptide of corin for pro-ANP processing, we constructed a soluble corin, EKshortCorin, that consists of only the protease domain and contains an enterokinase (EK) recognition sequence at the conserved activation cleavage site. After being activated by EK, EKshortCorin exhibited catalytic activity toward chromogenic substrates but failed to cleave pro-ANP, indicating that certain domain structures in the propeptide are required for pro-ANP processing. We then constructed a series of corin deletion mutants and studied their functions in pro-ANP processing. Compared with that of the full-length corin, a corin mutant lacking frizzled 1 domain exhibited ϳ40% activity, whereas corin mutants lacking single LDLR repeat 1, 2, 3, or 4 had ϳ49, ϳ12, ϳ53, and ϳ77% activity, respectively. We also made corin mutants with a single mutation at a conserved Asp residue that coordinates Ca 2؉ -binding in LDLR repeats 1, 2, 3, or 4 (D300Y, D336Y, D373Y, and D410Y) and showed that these mutants had ϳ25, ϳ11, ϳ16, and ϳ82% pro-ANP processing activity, respectively. Our results indicate that frizzled 1 domain and LDLR repeats 1-4 are important structural elements for corin to recognize its physiological substrate, pro-ANP.

Corin Mutation R539C from Hypertensive Patients Impairs Zymogen Activation and Generates an Inactive Alternative Ectodomain Fragment

“…The results are consistent with previous findings that the Fz1 and LDLR1-5 domains, which precede the Fz2 domain ( Fig. 2A), are required for pro-ANP processing (41). It is interesting that all corin fragments from autocleavage identified so far are biologically inactive, suggesting that autocleavage may serve as a mechanism to negatively regulate corin activity.…”

Extreme hyperopia is the result of null mutations inMFRP, which encodes a Frizzled-related protein

“…However, this idea is still speculative, because MFRP binding to Wnt proteins has yet to be demonstrated. Other roles are suggested by its closest CRD homologue, corin, a membranebound protease that cleaves the precursor of atrial natriuretic factor (28). Although MFRP has no obvious peptidase catalytic site, involvement in proteolytic pathways is also suggested by two Tolloid repeat units, each of which is comprised of globular domains related to cubulin and the low-density lipoprotein receptor (Fig.…”

Corin Is Present in the Normal Human Heart, Kidney, and Blood, with Pro–B-Type Natriuretic Peptide Processing in the Circulation

“…Corin consists of 1042 amino acids with an integral transmembrane domain near the N-terminus. Although the transmembrane domain of corin is not required for activity, the C-terminal trypsine-like protease domain is not sufficient for biological cleavage activity (10 ). Increasing attention on proBNP has occurred based on reports that it is increased in the plasma of humans with advanced heart failure (HF) (11,12 ).…”