Dataset Information

The Plethora of Angiotensin-Converting Enzyme Substrates in Mouse Plasma

ABSTRACT: Angiotensin converting enzyme (ACE) is known for converting inactive angiotensin I into the potent vasoconstrictor angiotensin II, playing a critical role in blood pressure regulation. However, there is evidence that the dicarboxypeptidase activity of ACE is also essential for other physiological processes likely through processing of various peptide substrates. This study used mass spectrometry for the comprehensive detection and identification of natural substrates and products of ACE within the mouse plasma peptidome. The plasma peptidome of ACE KO mice was obtained through a multi-step purification process which included organic TCA precipitation as well as size exclusion and reversed phase chromatography. The obtained complex mixture of endogenous peptides was then subjected to in vitro cleavage by ACE. ACE-treated and untreated samples were then analyzed by LC/MS on an Orbitrap mass spectrometer, followed by alignment of MS1 data by Progenesis QI software. The MS1 signals that gained or lost intensity after treatment with ACE, were considered as possible products and substrates of ACE, respectively, and were selected for a targeted MS/MS analysis, and subsequently identified with PEAKS 8.5 and Proteome Discoverer software. Results. Close to 250 natural peptides were identified as possible substrates and products of ACE, demonstrating the high promiscuity of the enzyme. The use of internal standards as well as detection of some expected endogenous peptides, such as angiotensin II and bradykinin, supported the validity of the approach. Some of the newly identified substrates of ACE are known for their biological activities. For example, a fragment of complement C3, the 17-amino acid peptide C3f, exhibits spasminogenic activity and was processed by ACE. ACE cleavage of select peptides was further confirmed in vitro. Also, concentrations of ACE substrates in plasma from mice with variant genetic ACE domain backgrounds were determined by LC/MS using multiple reaction monitoring on a triple quadrupole mass spectrometer. The in vivo results were consistent with the in vitro results, in the sense that higher levels of the ACE substrates were observed when the respective processing domain was knocked out. The use of transgenic mice as well as ACE with single active domain allowed clarifying the ACE domain selectivity towards individual peptide substrates. This study resulted in creation of a library of substrates and products of ACE that can be further tested for their biological function and can help to elucidate the link between ACE and the numerous physiological effects attributed to its activity.

INSTRUMENT(S): Orbitrap Fusion

ORGANISM(S): Mus Musculus (mouse)

TISSUE(S): Blood Plasma

SUBMITTER: Margarita (Rita) Semis

LAB HEAD: Markus Kalkum

PROVIDER: PXD010258 | Pride | 2019-11-12

REPOSITORIES: Pride

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The Plethora of Angiotensin-Converting Enzyme-Processed Peptides in Mouse Plasma.

Semis Margarita M Gugiu Gabriel B GB Bernstein Ellen A EA Bernstein Kenneth E KE Kalkum Markus M

Analytical chemistry 20190507 10

Angiotensin-converting enzyme (ACE) converts angiotensin I into the potent vasoconstrictor angiotensin II, which regulates blood pressure. However, ACE activity is also essential for other physiological functions, presumably through processing of peptides unrelated to angiotensin. The goal of this study was to identify novel natural substrates and products of ACE through a series of mass-spectrometric experiments. This included comparing the ACE-treated and untreated plasma peptidomes of ACE-kno ...[more]

PMID: 31021607

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Project description:Extracellular senile plaques of amyloid beta (Abeta) are a pathological hallmark in brain of patients with Alzheimer`s Disease (AD). Abeta is generated by the amyloidogenic processing of the amyloid precursor protein (APP). Concomitant to Abeta load, AD brain is characterized by an increase in protein level and activity of the angiotensin-converting enzyme (ACE). ACE inhibitors are a widely used class of drugs with established benefits for patients with cardiovascular disease. However, the role of ACE and ACE inhibition in the development of Abeta plaques and the process of AD-related neurodegeneration is not clear since ACE was reported to degrade Abeta. To investigate the effect of ACE inhibition on AD-related pathomechanisms, we used Tg2576 mice with neuron-specific expression of APPSwe as AD model. From 12 months of age, substantial Abeta plaque load accumulates in the hippocampus of Tg2576 mice as a brain region, which is highly vulnerable to AD-related neurodegeneration. The effect of central ACE inhibition was studied by treatment of 12 month-old Tg2576 mice for six months with the brain penetrating ACE inhibitor captopril. At an age of 18 months, hippocampal gene expression profiling was performed of captopril-treated Tg2576 mice relative to untreated 18 month-old Tg2576 controls with high Abeta plaque load. As an additional control, we used 12 month-old Tg2576 mice with low Abeta plaque load. Whole genome microarray gene expression profiling revealed gene expression changes induced by the brain-penetrating ACE inhibitor captopril, which could reflect the neuro-regenerative potential of central ACE inhibition. Microarray gene expression profiling was performed of hippocampi isolated from aged, 18 month-old Tg2576 (APPSwe-transgenic) AD mice with high Abeta plaque load relative to age-matched Tg2576 mice, which were treated for 6 months with the centrally active ACE inhibitor captopril. Another study group consisted of 12 month-old Tg2576 mice with low Abeta plaque load. In total, three study groups were analyzed, i.e. (i) 18 month-old untreated Tg2576 mice with high Abeta plaque load, (ii) age-matched Tg2576 mice treated for 6 months with the brain-penetrating ACE inhibitor captopril (20 mg/kg body weight/day in drinking water), and (iii) untreated 12 month-old Tg2576 mice with low Abeta plaque load reflecting the time point when captopril treatment was initiated. Two biological replicates were made of each group, and total hippocampal RNA of four mice was pooled for one gene chip.

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