Conformational fingerprint of blood and tissue ACEs: Personalized approach

Abstract

BackgroundThe pattern of binding of monoclonal antibodies (mAbs) to 18 epitopes on human angiotensin I-converting enzyme (ACE)–“conformational fingerprint of ACE”–is a sensitive marker of subtle conformational changes of ACE due to mutations, different glycosylation in various cells, the presence of ACE inhibitors and specific effectors, etc.Methodology/Principal findingsWe described in detail the methodology of the conformational fingerprinting of human blood and tissue ACEs that allows detecting differences in surface topography of ACE from different tissues, as well detecting inter-individual differences. Besides, we compared the sensitivity of the detection of ACE inhibitors in the patient’s plasma using conformational fingerprinting of ACE (with only 2 mAbs to ACE, 1G12 and 9B9) and already accepted kinetic assay and demonstrated that the mAbs-based assay is an order of magnitude more sensitive. This approach is also very effective in detection of known (like bilirubin and lysozyme) and still unknown ACE effectors/inhibitors which nature and set could vary in different tissues or different patients.Conclusions/SignificancePhenotyping of ACE (and conformational fingerprinting of ACE as a part of this novel approach for characterization of ACE) in individuals really became informative and clinically relevant. Appreciation (and counting on) of inter-individual differences in ACE conformation and accompanying effectors make the application of this approach for future personalized medicine with ACE inhibitors more accurate. This (or similar) methodology can be applied to any enzyme/protein for which there is a number of mAbs to its different epitopes.

Tissue ACE phenotyping in prostate cancer

“…Cell and tissue specificity of these enzymes suggests that each type (including probably malignant cells) have a unique “sialome” which may be used to document cell origin or pathology [47]. Our hypothesis, that observed changes in binding of mAb 3F10 to ACE from BPH and PC prostate tissues (Figure 4) are due to hypersialylation of ACE molecules is supported by the finding that this very mAb bind better to plasma ACE than to lung ACE (Figure 10A in [35], and plasma ACE is known to be more sialylated than its “parent” lung enzyme as a result of elimination of less sialylated proteins from the blood by liver lectins [48].…”

“…As a result, the ratio of the rates of hydrolysis of these two substrates (ZPHL/HHL ratio) serves as a characteristic of a definite ACE form: for somatic two-domain human ACE it is about 1-1.5, for N domain – 5-7, and C domain – 0.6-0.8 [27]. The ZPHL/HHL ratio used primarily to detect the presence of common ACE inhibitors taken as a drug in patients’ blood at the time of blood sampling [27, 34, 35]. This parameter can also help to detect inactivation or inhibition of a separate domain, as the increase of this ratio can indicate inactivation/inhibition of the C domain, while the decrease of this ratio may be an indicator for inactivation/inhibition of N domain [27].…”

Human angiotensin I‐converting enzyme study by surface‐enhanced Raman spectroscopy

“…The pattern of glycosylation of ACE produced in various tissues and, therefore, ACE ability to bind monoclonal antibodies to different regions on the protein globule can vary significantly [29,[32][33][34][35] due to the differences in posttranslational modification of the enzyme in different types of cells. Thus, ACE can be considered as a perspective biomarker of various diseases and by now identification of cell-specific ACE in the blood by the panel of monoclonal antibodies was successfully demonstrated on the examples of sarcoidosis [28,36] and Gaucher disease.…”

Tissue ACE phenotyping in lung cancer

“…We hypothesized that particular differences in mAbs 1B8 and 3F10 binding to lung cancer ACE (Fig 4) may result from greater extent of sialylation of glycan in Asn731 in tumor. This possibility arise from the observation that these very mAbs better bind to plasma ACE than to lung ACE (Fig 10A in [55]), and plasma ACE is known to be more sialylated than its “parent” lung enzyme as a result of elimination of unsialylated proteins from plasma by liver lectins [56].…”