A mechanism for hereditary angioedema with normal C1 inhibitor: An inhibitory regulatory role for the factor XII heavy chain

Ivan Ivanov, Anton Matafonov, Mao Fu Sun, Bassem M. Mohammed, Qiufang Cheng, S. Kent DIckeson, Suman Kundu, Ingrid M. Verhamme, Andras Gruber, Keith McCrae, David Gailani

Research output: Contribution to journalArticlepeer-review

36 Scopus citations


The plasma proteins factor XII (FXII) and prekallikrein (PK) undergo reciprocal activation to the proteases FXIIa and kallikrein by a process that is enhanced by surfaces (contact activation) and regulated by the serpin C1 inhibitor. Kallikrein cleaves high-molecularweight kininogen (HK), releasing the vasoactive peptide bradykinin. Patients with hereditary angioedema (HAE) experience episodes of soft tissue swelling as a consequence of unregulated kallikrein activity or increased prekallikrein activation. AlthoughmostHAE cases are caused by reduced plasma C1-inhibitor activity, HAE has been linked to lysine/arginine substitutions for Thr309 in FXII (FXII-Lys/Arg309). Here, we show that FXII-Lys/Arg309 is susceptible to cleavage after residue 309 by coagulation proteases (thrombin and FXIa), resulting in generation of a truncated form of FXII (δFXII). The catalytic efficiency of δFXII activation by kallikrein is 15-fold greater than for full-length FXII. The enhanced rate of reciprocal activation of PK and δFXII in human plasma and in mice appears to overwhelm the normal inhibitory function of C1 inhibitor, leading to increased HK cleavage. In mice given human FXII-Lys/Arg309, induction of thrombin generation by infusion of tissue factor results in enhanced HK cleavage as a consequence of δFXII formation. The effects of δFXII in vitro and in vivo are reproduced when wild-type FXII is bound by an antibody to the FXII heavy chain (HC; 15H8). The results contribute to our understanding of the predisposition of patients carrying FXII-Lys/Arg309 to angioedema after trauma, and reveal a regulatory function for the FXII HC that normally limits PK activation in plasma.

Original languageEnglish (US)
Pages (from-to)1152-1163
Number of pages12
Issue number10
StatePublished - 2019

ASJC Scopus subject areas

  • Biochemistry
  • Immunology
  • Hematology
  • Cell Biology


Dive into the research topics of 'A mechanism for hereditary angioedema with normal C1 inhibitor: An inhibitory regulatory role for the factor XII heavy chain'. Together they form a unique fingerprint.

Cite this