Dominant-negative SERPING1 variants cause intracellular retention of C1 inhibitor in hereditary angioedema
Didde Haslund, … , Lene N. Nejsum, Jacob Giehm Mikkelsen
Didde Haslund, … , Lene N. Nejsum, Jacob Giehm Mikkelsen
Published November 6, 2018
Citation Information: J Clin Invest. 2019;129(1):388-405. https://doi.org/10.1172/JCI98869.
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Dominant-negative SERPING1 variants cause intracellular retention of C1 inhibitor in hereditary angioedema

Abstract

Hereditary angioedema (HAE) is an autosomal dominant disease characterized by recurrent edema attacks associated with morbidity and mortality. HAE results from variations in the SERPING1 gene that encodes the C1 inhibitor (C1INH), a serine protease inhibitor (serpin). Reduced plasma levels of C1INH lead to enhanced activation of the contact system, triggering high levels of bradykinin and increased vascular permeability, but the cellular mechanisms leading to low C1INH levels (20%–30% of normal) in heterozygous HAE type I patients remain obscure. Here, we showed that C1INH encoded by a subset of HAE-causing SERPING1 alleles affected secretion of normal C1INH protein in a dominant-negative fashion by triggering formation of protein-protein interactions between normal and mutant C1INH, leading to the creation of larger intracellular C1INH aggregates that were trapped in the endoplasmic reticulum (ER). Notably, intracellular aggregation of C1INH and ER abnormality were observed in fibroblasts from a heterozygous carrier of a dominant-negative SERPING1 gene variant, but the condition was ameliorated by viral delivery of the SERPING1 gene. Collectively, our data link abnormal accumulation of serpins, a hallmark of serpinopathies, with dominant-negative disease mechanisms affecting C1INH plasma levels in HAE type I patients, and may pave the way for new treatments of HAE.

Authors

Didde Haslund, Laura Barrett Ryø, Sara Seidelin Majidi, Iben Rose, Kristian Alsbjerg Skipper, Tue Fryland, Anja Bille Bohn, Claus Koch, Martin K. Thomsen, Yaseelan Palarasah, Thomas J. Corydon, Anette Bygum, Lene N. Nejsum, Jacob Giehm Mikkelsen

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Figure 10

Increased C1INH secretion after lentiviral delivery of WT SERPING1 gene models HAE gene therapy in fibroblasts from patients carrying a dominant-negative disease allele (SERPING1[c.551_685del]).

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Increased C1INH secretion after lentiviral delivery of WT SERPING1 gene ...
(A) HeLa-WT and HeLa-c.551_685del cell populations (3 of each) were created by transduction of naive HeLa cells with lentiviral vectors encoding normal C1INH or C1INHGly162_Pro206del. Stably transduced and naive HeLa cells were reseeded and transduced with lentiviral vectors encoding eGFP or normal C1INH. Transduction of each of the 3 cell populations was carried out in triplicate (n = 3) and the medium was pooled for each transduced cell population prior to C1INH measurements. For the naive cell line, cells were transduced and medium pooled prior to C1INH measurement, resulting in only a single data point for each treatment. (B) Control and patient-derived fibroblasts were transduced with lentiviral vectors encoding normal C1INH or eGFP as a control. Transductions were carried out in triplicate (n = 3). (A and B) Data are mean ± SEM. **P < 0.01, ***P < 0.001, compared with untransduced cells in each group. NS indicates lack of statistical significance between untransduced and LV/PGK-eGFP–treated groups. Statistical analyses were performed by 1-way ANOVA with Dunnett’s multiple comparison test. (B) Similar results were seen in at least 2 independent experiments. LV, lentiviral vectors.