Extracellular HtrA2 Induces Apoptosis in Human Umbilical Vein Endothelial Cells

Abstract

The serine protease high-temperature-required protein A2 (HtrA2) has been identified as a key intracellular molecule promoting apoptosis in cells during ischemia reperfusion (IR) injury. IR injury in ST-segment elevation myocardial infarction (STEMI) contributes to overall myocardial damage. HtrA2 has further been shown to be significantly increased in the serum of patients with STEMI. In the present pilot study, we use human umbilical vein endothelial cells (HUVECs) to investigate whether extracellular HtrA2 induces apoptosis using Annexin V staining. Furthermore, we examine whether HtrA2 is released extracellularly after staurosporine-induced apoptosis using ELISA. We find that HtrA2 is released upon induction of apoptosis by staurosporine into the cell culture medium. Furthermore, treatment of HUVECs with extracellular HtrA2-induces apoptosis, while the addition of anti-HtrA2 antibodies reduces both HtrA2- and staurosporine-induced endothelial cell apoptosis. In conclusion, we show here that extracellular HtrA2 induces apoptosis in human endothelial cells, although the exact molecular mechanisms have to be investigated in future.

Mitochondrial quality control proteases and their modulation for cancer therapy

“…Mechanistically, HTRA2 was directly bound to PDK1 and further inhibited the PI3K/AKT signaling pathway, which affected mitochondrial autophagy and regulated cell apoptosis. The above data further illustrated HTRA2 as a potential therapeutic target for cancer 131,175 . Interestingly, Chaganti's group identified the endogenous substances HAX‐1 and GRIM‐19 as metabotropic regulators of HTRA2 and elucidated the combinational mode, which provided data support for the development of HTRA2 activators.…”

“…The above data further illustrated HTRA2 as a potential therapeutic target for cancer. 131,175 Interestingly, Chaganti's group identified the endogenous substances HAX-1 and GRIM-19 as metabotropic regulators of HTRA2 and elucidated the combinational mode, which provided data support for the development of HTRA2 activators. Specifically, HTRA2 is a trimeric pyramidal protease, and the active site is inside the pyramid, contributing to a necessary conformational change before binding to the substrate.…”

Role of high-temperature requirement serine protease A 2 in rheumatoid inflammation

“…HtrA2 is an apoptosis-triggering protein that is discharged from the mitochondria into the cytosol in response to an apoptotic signal [ 17 , 18 ]. A recent study showed that HtrA2 expression is detectable in the extracellular space of human umbilical vein endothelial cells during apoptosis [ 19 ]. To determine whether HtrA2 is released by primary synoviocytes, we stimulated FLSs with tunicamycin or thapsigargin as an ER stress inducer.…”

“…We observed the release of HtrA2 from mitochondria into the culture medium following treatment with an ER stress inducer. Several scientists have postulated that during apoptosis, cytochrome c is released from the mitochondria into the cytosol and ultimately into the extracellular space [ 31 – 33 ]; however, the release of HtrA2 into the extracellular space during apoptosis has yet to be established [ 19 ]. In the present study, we demonstrated that HtrA2 release from RA FLSs into the extracellular environment was implicated in ER-stress-induced apoptosis.…”