Cloning and Characterization of cDNA for Inter-α-Trypsin Inhibitor Family Heavy Chain-Related Protein (IHRP), a Novel Human Plasma Glycoprotein

Abstract

The cDNA encoding inter-alpha-trypsin inhibitor family heavy chain-related protein (IHRP) was cloned from human liver cDNA libraries. Oligonucleotide primers of human liver cDNA for PCR were constructed from internal amino acid sequences obtained with proteolytic fragments of IHRP. The amplified cDNA served as a hybridization probe for the screening of human liver cDNA libraries. The cDNA of 2,977 bp contained an entire reading frame coding 930 amino acids. The N-terminal 28 residues corresponded to a signal peptide for secretion. The N-terminal 600 residues of the mature form exhibited considerable homology to those of ITI heavy chains, while the C-terminal 300 residues showed no homology with the heavy chains and low homology with ATP-dependent proteases. IHRP was readily cleaved into 85- and 35-kDa fragments when plasma was incubated at 37 degrees C. The cleaved site, Arg-Arg-Leu, was within a proline-rich region. Northern blot analysis of poly(A) RNAs from various human tissues only showed hybridization to liver RNA.

Quantitative Measurement of the Novel Human Plasma Protein, IHRP, by Sandwich ELISA.

“…those of bradykinin and angiotensin II. 11,12) However, we could not detect any activities of IHRP and its fragments in the pharmacological assays (unpublished data). The other interesting aspect of IHRP is its high sequence homology to the mRNA which was induced in the porcine liver after resuscitation from cardiogenic shock.…”

“…1,2) In a search of the nucleotide sequence homology of IHRPcDNA, we found that the nucleotide sequence registered as porcine ITI cDNA in LASL-GDB (Gen Bank) data base showed significant homology (83%) to that of IHRP cDNA. 11) Since this sequence homology was higher than those (49-57%) of mRNAs among IHRP and ITI family heavy chains, we thought that the registered porcine ITI mRNA, which was detected as the inducible mRNA in the liver after resuscitation from cardiogenic shock, 13) was the species counterpart of human IHRP mRNA rather than porcine ITI family heavy chain mRNA.…”

“…9,10) In spite of the sequence similarity, IHRP did not form a complex with bikunin because of the deletion of the consensus sequence (DPHFII) for the cleavage of the C-terminal fragment and the attachment to the chondroitin sulfate sugar chain of bikunin. 11,12) IHRP was readily cleaved to the N-terminal 85-kDa-fragment and the C-terminal 35-kDa fragment by plasma kallikrein. 1,2) The N-terminal 85-kDa fragment was further cleaved to the N-terminal 57-kDa fragment and to unidentified small fragments.…”

Pig Major Acute-Phase Protein and apolipoprotein A-I responses correlate with the clinical course of experimentally induced African Swine Fever and Aujeszky's disease

“…In previous works carried out at our laboratory, a new 120 kDa plasma glycoprotein, which was denominated Pig Major Acute Phase protein (Pig-MAP), was identified as a relevant acute phase protein in animals under turpentine-induced inflammation [17,21]. This protein was also referred to as PK-120 [26] or IHRP [36] being subsequently denominated ITIH4 (heavy chain 4 of the inter-alpha trypsin inhibitor family) [5]. Increases in the ITIH4 concentration under different physio-pathological situations have been reported in pigs [18,21,38], rats [10,17], bovines [30], humans [29,43] and mice [12].…”

Hypercholesterolemia associated with splice-junction variation of inter-α-trypsin inhibitor heavy chain 4 (ITIH4) gene

“…All four heavy chain precursors and the resulting mature heavy chains harbor a so-called von Willebrand type-A (vWA) domain (Chan P et al 1995, Bork P et al 1991. Only the heavy chain 4 precursor polypeptide harbors a plasma Kallikrein-released bradykinin-like domain on its C-terminal sequence (Nishimura H et al 1995) and a domain with some similarity to the ATP-dependent proteases (Saguchi K et al 1995). Although the suspected link between functional changes of ITIH4 protein and plasma T-Cho metabolism was not a commonly expected one, it may have unidentified functions in regulation of cholesterol synthesis and catabolism in the liver.…”