Serine Carboxypeptidase SCPEP1 and Cathepsin A Play Complementary Roles in Regulation of Vasoconstriction via Inactivation of Endothelin-1

Abstract

The potent vasoconstrictor peptides, endothelin 1 (ET-1) and angiotensin II control adaptation of blood vessels to fluctuations of blood pressure. Previously we have shown that the circulating level of ET-1 is regulated through its proteolytic cleavage by secreted serine carboxypeptidase, cathepsin A (CathA). However, genetically-modified mouse expressing catalytically inactive CathA S190A mutant retained about 10–15% of the carboxypeptidase activity against ET-1 in its tissues suggesting a presence of parallel/redundant catabolic pathway(s). In the current work we provide direct evidence that the enzyme, which complements CathA action towards ET-1 is a retinoid-inducible lysosomal serine carboxypeptidase 1 (Scpep1), a CathA homolog with previously unknown biological function. We generated a mouse strain devoid of both CathA and Scpep1 activities (DD mice) and found that in response to high-salt diet and systemic injections of ET-1 these animals showed significantly increased blood pressure as compared to wild type mice or those with single deficiencies of CathA or Scpep1. We also found that the reactivity of mesenteric arteries from DD mice towards ET-1 was significantly higher than that for all other groups of mice. The DD mice had a reduced degradation rate of ET-1 in the blood whereas their cultured arterial vascular smooth muscle cells showed increased ET-1-dependent phosphorylation of myosin light chain 2. Together, our results define the biological role of mammalian serine carboxypeptidase Scpep1 and suggest that Scpep1 and CathA together participate in the control of ET-1 regulation of vascular tone and hemodynamics.

Lysosomal Cathepsin A Plays a Significant Role in the Processing of Endogenous Bioactive Peptides

“…Although, the markedly increased endothelin-1-specific immunoreactivity has been demonstrated in CTSA deficient galactosialidosis patient's brain, we did not observe any difference neither in brain nor in liver from CTSA S190A mice using ELISA (Itoh et al, 2000). We also speculate that higher expression of other carboxypeptidases such as Scpep1 may contribute modulating the catabolic proteolysis of Endothelin-I in these tissues (Pshezhetsky and Hinek, 2009; Pan et al, 2014). …”

Chemical Proteomic Analysis of Serine Hydrolase Activity in Niemann-Pick Type C Mouse Brain

“…These enzymes are lysosomal proteins, which is in line with the important role of NPC1 in lysosomes. SCPEP1 shows homology with CTSA ( Kollmann et al, 2009 ) and a study with double knockout of SCPEP1 and CTSA suggests they share the same peptide substrate ( Pan et al, 2014 ). Single knockout of SCPEP1 in mice resulted in viable mice without lysosomal impairment ( Kollmann et al, 2009 ).…”

Mice, double deficient in lysosomal serine carboxypeptidases Scpep1 and Cathepsin A develop the hyperproliferative vesicular corneal dystrophy and hypertrophic skin thickenings

“…Mice containing Ser190Ala point mutation in the CathA active site (CathAS190A strain) and those with the Scpep1 gene interrupted by gene-trap technology (Scpep12/2 strain) were generated as previously described[ 21 , 22 ]. Mice were housed in an enriched environment with continuous access to food and water, under constant temperature and humidity, on a 12 h light/dark cycle.…”

“…Previous studies from our laboratory defined a novel pathway for enzymatic inactivation of circulating ET-1 involving two lysosomal/secreted serine carboxypeptidases, cathepsin A (CathA) and serine carboxypeptidase 1 (Scpep1)[ 20 , 21 ]. In particular, we showed that mice with double deficiency of CathA and Scpep1 developed a persisted hypertension and demonstrated a prolonged half-life of circulating ET-1 as well as a more pronounced vasoconstriction in response to low pharmacological doses of this peptide[ 21 ].…”