Alpha-1-antichymotrypsin variant detected by PCR-single strand conformation polymorphism (PCR-SSCP) and direct sequencing

alpha 1-antitrypsin TAQ I polymorphism and alpha 1-antichymotrypsin mutations in patients with obstructive pulmonary disease

Obstructive pulmonary disease is a multifactorial condition deriving from the interaction of environmental and genetic factors. From biochemical knowledge of the basis of the disease, alpha 1-antitrypsin and alpha 1-antichymotrypsin are considered two likely candidate genes. We therefore designed an association study comprising 232 unrelated Italian individuals divided as follows: 89 individuals with obstructive lung disease (66 with COPD and 23 with disseminated bronchiectasis) and 143 controls (45 patients with non-obstructive lung disease and 98 healthy individuals). We screened for Taq I (G1237A) polymorphism of the alpha 1-antitrypsin gene as well as the rare variants Bonn-1 (Pro229Ala), Bochum-1 (Leu55Pro), Isehara-1 (Met389Val) and Isehara-2 (1258delAA), and the common signal peptide polymorphism Thr-15Ala of the alpha 1-antichymotrypsin gene. The frequencies of Taq I G1237A alleles were 11.7 and 10.8% in obstructed patients and controls, respectively (P = 0.43), while those of signal peptide Thr-15Ala alleles were 51.6 and 50.3% in obstructed patients and controls, respectively (P = 0.42). We conclude that alpha 1-antitrypsin Taq I polymorphism and alpha 1-antichymotrypsin Thr-15Ala mutation are not major genetic risk factors for the development of obstructive lung disease in Italian patients. The alpha 1-antichymotrypsin rare variants were not detected: our results do not exclude the possibility that other alpha 1-antichymotrypsin gene mutations might be present in Italian obstructed patients but, if so, these genetic defects must be rare.

Molecular studies define the primary structure of alpha1-antichymotrypsin (ACT) protease inhibitor in Alzheimer's disease brains. Comparison of act in hippocampus and liver

An alpha1-antichymotrypsin-like serpin has been implicated in Alzheimer's disease (AD) based on immunochemical detection of alpha1-antichymotrypsin (ACT) in amyloid plaques from the hippocampus of AD brains. The presence of neuroendocrine isoforms of ACTs and reported variations in human liver ACT cDNA sequences raise the question of the molecular identity of ACT in brain. In this study, direct reverse transcription-polymerase chain reaction and cDNA sequencing indicate that the hippocampus ACT possesses the reactive site loop that is characteristic of serpins, with Leu as the predicted P1 residue interacting with putative chymotrypsin-like target proteases. The deduced primary sequence of the human hippocampus ACT possesses more than 90% homology with reported primary sequences for the human liver ACT. Moreover, identical ACT primary sequences deduced from the cDNAs were demonstrated in the hippocampus of control and AD brains. Northern blots showed that ACT mRNA expression in hippocampus was 900 times lower than that in liver. Also, hippocampus and liver ACT proteins demonstrated differential sensitivities to deglycosylation. Overall, reverse transcription-polymerase chain reaction combined with cDNA and primary sequence analyses have defined the molecular identity of human hippocampus ACT in control and AD brains. The determined reactive site loop domain of hippocampus ACT will allow prediction of potential target proteases inhibited by ACT in AD.

The defective secretion of a naturally occurring alpha-1-antichymotrypsin variant with a frameshift mutation

A newly found variant alpha-1-antichymotrypsin (ACT), ACT Isehara-2, has a deletion of two bases (AA) at codon 391 near the carboxyl terminus. This frameshift mutation caused a change in the amino acid sequence and generated 10 extra amino acids (408 amino acids total) [Tsuda, M., Sei, Y., Matsumoto, M., Kamiguchi, H., Yamamoto, Y., Shinohara, Y., Igarashi, T. & Yamamura, M. (1992) Hum. Genet. 91. 467-468]. The serum ACT levels in three unrelated heterozygotes with this mutant ACT gene were 37% 49% and 54% that of the normal individuals. To examine the reduced serum levels, the normal ACT and the mutant ACT created by site-directed mutagenesis were transfected into COS-7 cells for comparison. The value for the retention rate (intracellular ACT/total ACT) was apparently higher in the cells expressing mutant ACT Isehara-2 than those bearing the normal gene. In the pulse-chase experiments, the secretion of the synthesized mutant ACT into the medium was not observed, whereas the normal ACT was mostly secreted as a 64-kDa form. The endoglycosidase H digestion and an electron microscopic analysis indicated that the retained mutant ACT was present in the endoplasmic reticulum. These results provide the biochemical basis for the decreased serum ACT level of individuals with ACT Isehara-2, and suggest the importance of the carboxyl-terminal region for its secretion.