Protoporphyrins Enhance Oligomerization and Enzymatic Activity of HtrA1 Serine Protease

• Type of Material: Article
• Authors: Hakryul Jo, Yale University; Victoria Patterson, Yale University; Sean Stoessel, Yale University; Josephine Hoh, Yale University; Chia-Yi Kuan, Emory University
• Language: English
• Date: 2014-12-15
• Publisher: Public Library of Science
• Publication Version: Final Published Version
• Copyright Statement: © 2014 Jo et al.
• License: Creative Commons Attribution 4.0 International
• Final Published Version (URL): http://dx.doi.org/10.1371/journal.pone.0115362
• Title of Journal or Parent Work: PLoS ONE
• ISSN: 1932-6203
• Volume: 9
• Issue: 12
• Start Page: e115362
• End Page: e115362
• Grant/Funding Information: The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.; This work was funded by Rosebay Medical Foundation and Yale Medical School Dean’s Research Fund. No URL is available.
• Keywords: Multidisciplinary Sciences; GENE; Science & Technology - Other Topics; FAMILY PROTEINS; THERAPY; OXYGEN; QUALITY CONTROL; TARGETS; CANCER; SERUM-ALBUMIN; Science & Technology; MACULAR DEGENERATION; SMALL-VESSEL DISEASE
• Research Categories: Biology, Molecular; Health Sciences, Pathology; Biology, Physiology

Abstract

High temperature requirement protein A1 (HtrA1), a secreted serine protease of the HtrA family, is associated with a multitude of human diseases. However, the exact functions of HtrA1 in these diseases remain poorly understood. We seek to unravel the mechanisms of HtrA1 by elucidating its interactions with chemical or biological modulators. To this end, we screened a small molecule library of 500 bioactive compounds to identify those that alter the formation of extracellular HtrA1 complexes in the cell culture medium. An initial characterization of two novel hits from this screen showed that protoporphyrin IX (PPP-IX), a precursor in the heme biosynthetic pathway, and its metalloporphyrin (MPP) derivatives fostered the oligomerization of HtrA1 by binding to the protease domain. As a result of the interaction with MPPs, the proteolytic activity of HtrA1 against Fibulin-5, a specific HtrA1 substrate in age-related macular degeneration (AMD), was increased. This physical interaction could be abolished by the missense mutations of HtrA1 found in patients with cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL). Furthermore, knockdown of HtrA1 attenuated apoptosis induced by PPP-IX. These results suggest that PPP-IX, or its derivatives, and HtrA1 may function as co-factors whereby porphyrins enhance oligomerization and the protease activity of HtrA1, while active HtrA1 elevates the pro-apoptotic actions of porphyrin derivatives. Further analysis of this interplay may shed insights into the pathogenesis of diseases such as AMD, CARASIL and protoporphyria, as well as effective therapeutic development.