A. Zanichelli

C. Suffritti

D. Parolin

F. Perego

M. Cicardi

M.A. Wu

S. Berra

S. Caccia

English

AIR Universita degli studi di Milano

Page 10 of 39Allergy Asthma Clin Immunol 2019, 15(Suppl 4):45
O15 
A SERPING1 variant that causes C1-inhibitor de"ciency 
without hereditary angioedema
Silvia  Berra1, Chiara  Suﬀritti1, Andrea  Zanichelli1,2, Debora  Parolin1, 
Maddalena A. Wu1,2, Francesca  Perego3, Marco  Cicardi1,2, Sonia  Caccia1,*
1”L. Sacco” Department of Biomedical and Clinical Sciences, University 
of Milan, Milan, Italy; 2ASST Fatebenefratelli Sacco, Milan, Italy; 3Istituti 
Clinici Scientiﬁci Maugeri IRCCS, Milan, Italy 
Correspondence: Sonia Caccia (sonia.caccia@unimi.it)
Allergy, Asthma & Clinical Immunology 2019, 15(Suppl 4):O15
More than 400 mutations (around 25% de novo) in SERPING1 have 
been described to cause functional C1-inhibitor (C1-INH) de!ciency 
and hereditary angioedema (HAE). Angioedema symptoms and 
C1-INH de!ciency co-segregate within the families with autosomal 
dominant inheritance. Two promoter and two structural SERPING1 
variants escape this rule. These four mutations represent a recessive 
character: they cause the clinical phenotype of HAE only when present 
in homozygosity.
Here we describe variant g.22006G > A (p.Arg494Gln) in SERPING1, 
detected in 12 subjects from four families with C1-INH de!ciency and 
no HAE. The variant is located in a region of the molecule that is critical 
for regulating SERPIN conformational state.
Index cases in each family were identi!ed due to urticaria symptoms 
that prompted measurements of C1-INH and C4. In none of the four 
families there was evidence for inherited angioedema without wheals 
while inherited C1-INH and C4 de!ciency were clearly present. Inhibi-
tory function of C1-INH against C1s, kallikrein and FXIIa was below 
50% of normal. Repeated measurements of complement parameters 
in C1-INH de!ciency carriers, showed a degree of variability, which is 
never detected in typical C1-INH-HAE. When these subjects under-
went danazol treatment, complement parameters rapidly normalized. 
All C1-INH de!cient subjects in the four families, carried the mutation 
g.22006G > A (p.Arg494Gln) in SERPING1. When the mutant protein 
was expressed in a murine hepatoma cell line, analysis of the super-
natant failed to detect the protein, which was instead abundant in the 
insoluble fraction of cell lysate. We hypothesize that intracellular accu-
mulation is due to polymer formation.
Our !ndings indicate that p.Arg494Gln-C1-INH allows protein synthe-
sis, but impaired cytoplasmic secretion. The same condition seems to 
apply to the other SERPING1 structural variants that cause recessive 
forms of HAE. No homozygous p.Arg494Gln has ever been described 
and we cannot conclude that also this mutant leads to recessive HAE. 
However, variability of C1-INH plasma levels in this as in other variants 
that are clinically silent in heterozygous presentation, suggests a lower 
degree of impairment in the synthesis of functional C1-INH. Whether 
this is due to the mutant contributing to C1-INH function in plasma or 
to the mutant that has reduced trans-inhibition e"ect on the wild type 
allele remains to be elucidated.
The study was approved by Milano Area 1 Ethics Board, approval num-
ber 11846/2017. Informed consent to publish has been obtained from 
the patients.
O16 
Activation of complement MASP-3 in healthy donors 
and in patients with C1-inhibitor de"ciency
Gábor Oroszlán1, Gábor Pál2, Péter Závodszky1, Henriette  Farkas3, Péter 
Gál1, József Dobó1,*
1Institute of Enzymology, Research Centre for Natural Sciences, Hungarian 
Academy of Sciences, Budapest, Hungary; 2Department of Biochemistry, 
Eötvös Loránd University, Budapest, Hungary; 3Hungarian Angioedema 
Reference Center,  3rd Department of Internal Medicine, Semmelweis 
University, Budapest, Hungary 
Correspondence: József Dobó (dobo.jozsef@ttk.mta.hu)
Allergy, Asthma & Clinical Immunology 2019, 15(Suppl 4):O16
Activation of the lectin pathway of complement is initiated by 
mannose-binding lectin (MBL)-associated serine proteases 1 and 2 
(MASP-1 and MASP-2). MASP-1 and MASP-2 circulate in the blood as 
zymogens in complex with pattern recognition molecules (PRMs), 
such as MBL, other collectins, and !colins. The third serine protease of 
the lectin pathway (MASP-3), which is also complexed with PRMs, was 
shown to be the major physiological activator of pro-factor D (pro-FD) 
in the blood, linking the alternative and the lectin complement path-
ways. We have demonstrated earlier that only activated MASP-3 is 
capable of converting pro-FD to factor D (FD), and indeed the major 
form of MASP-3 in the blood is the active form. The activation mecha-
nism of MASP-3, however, remains unclear. In vitro MASP-1 can acti-
vate MASP-3, and C1-inhibitor is the major physiological regulator of 
MASP-1. We hypothesized that if MASP-1 is the physiological activator 
of MASP-3 then individuals with low C1-inhibitor levels would exhibit 
altered MASP-3 activation.
The activation state of endogenous MASP-3 was detected by Western 
blot, whereas in other experiments #uorescently labeled recombinant 
MASP-3 variants were used. We found that a signi!cant portion of full-
length, labeled MASP-3 became “activated” (cleaved) in hirudin-plasma 
in the matter of hours even when the inactive S664A variant was used. 
The activation was less e$cient, but still occurred, when the N-termi-
nally truncated catalytic fragment was used. On the other hand, we 
found that the ratio of active MASP-3 in type I HAE patients was virtu-
ally identical with that in healthy individuals, namely 82 ± 3%, versus 
81 ± 4%. This indicates that a protease other than MASP-1 is responsi-
ble for the activation of MASP-3. To con!rm this assumption we moni-
tored the cleavage of labeled MASP-3 in the presence or absence of a 
MASP-1-speci!c inhibitor. Again, no di"erence was observed.
In conclusion, our results imply that a protease is present in the blood 
that converts MASP-3 to the active form. The activation is not autoac-
tivation because the inactive variant got cleaved as well. Activation is 
more pronounced with the full length protein implying that binding 
of MASP-3 to PRMs might be necessary for e$cient activation. Activa-
tion of MASP-3 is probably carried out by a protease not inhibited by 
C1-inhibitor.
O17 
Simultaneous determination of human plasma serine proteases 
complexed with C1-inhibitor in vivo
Zsóﬁa  Jandrasics1,*, Erika Kajdácsi1,*#, Nóra  Veszeli2,4, Vera Makó4, Anna 
 Koncz1, Kinga Viktória Kőhalmi1, László  Cervenak1, Péter Gál3, József 
Dobó3, Steven de  Maat5, Coen  Maas5, Henriette  Farkas1,2, Lilian  Varga1,2
1Research Laboratory,  3rd Department of Internal Medicine, Semmelweis 
University, Budapest, Hungary; 2Hungarian Angioedema Reference 
Center,  3rd Department of Internal Medicine, Semmelweis University, 
Budapest, Hungary; 3Institute of Enzymology, Research Centre for Natural 
Sciences, Hungarian Academy of Sciences, Budapest, Hungary; 4MTA-SE 
Fig. 1 Diagram of counts of subjects reporting the speciﬁc STP 
agents (choices were “C1Inh”, “Icatibant”, “Ecallantide”, “rC1Inh”, 
“other”). Of the 120 subjects who received STP, a total of 91 subjects 
reported receiving C1Inh [human] as STP (which includes 79 subjects 
exclusively on C1Inh [human], 1 subject on rC1Inh + C1Inh, 7 on 
Icatibant + C1Inh, 3 on Other + C1Inh, and 1 on Other + Icati-
bant + C1Inh.). 10 received Icatibant only as STP, 1 received Ecallan-
tide only, and 1 received rC1Inh only. 17 subjects reported receiving 
other STP agent (choices were “C1Inh. 130 subjects did not receive 
STP


A SERPING1 variant that causes C1-inhibitor deficiency without hereditary angioedema

https://air.unimi.it/bitstream/2434/687850/2/o15_s13223-019-0355-0.pdf

A SERPING1 variant that causes C1-inhibitor deficiency without hereditary angioedema

Abstract

Similar works

Full text

Available Versions

AIR Universita degli studi di Milano