Evaluation of the cardiac isoform of alpha2-macroglobulin as a factor inducing cardiac hypertrophy.
Earlier studies from our laboratory showed that a 182-kDa high-molecular-weight protein appeared during early stages of development of cardiac hypertrophy in animals subjected to aortic constriction. Later it was confirmed that this protein is a cardiac isoform of alpha2-macroglobulin belonging to the macroglobulin family. Furthermore, it has been demonstrated that direct injection of the purified 182-kDa protein intravenously (through the tail vein) into the normal animals led to the development of cardiac hypertrophy. It was accompanied by enlargement of cardiac myocytes and induction of beta-myosin heavy chain (MHC) and MLC-2 gene expression. Multiple injections of 182-kDa protein-specific polyclonal antibody into the circulation of aorta-constricted animals completely abolished the development of hypertrophy and downregulated the expression of beta-MHC and myosin light chain (MLC)-2. The full-length cDNA of the 182-kDa protein cloned in eukaryotic expression vector, namely, pcDNA 3.1(-) could induce cardiac hypertrophy upon direct injection into rat heart. Hypertrophy was monitored by determining the heart weight/body weight ratio and also by Northern blot analysis of muscle-specific marker genes such as beta-MHC, MLC-2, and antrial natriuretic factor. Also, induction of promoter activity of beta-MHC and c-fos genes analyzed by chloramphenicol acetyl transferase assay confirmed the induction of cardiac hypertrophy upon direct injection of the full-length cDNA of the 182-kDa protein.
Rajamanickam
Chellam
C
Center for Advanced Studies in Functional Genomics, Department of Biochemistry, Madurai Kamaraj University, India.
Jeejabai
Radhakrishnan
R
D000818:Animals; D001024:Aortic Valve Stenosis / Q000150:complications / Q000503:physiopathology; D015415:Biomarkers; D024722:Cardiac Myosins / Q000235:genetics; D006332:Cardiomegaly / Q000139:chemically induced* / Q000235:genetics / Q000473:pathology*; D048429:Cell Size; D015500:Chloramphenicol O-Acetyltransferase / Q000235:genetics; D018076:DNA, Complementary; D015536:Down-Regulation; D005240:Feasibility Studies; D015870:Gene Expression; D018014:Gene Transfer Techniques; D007275:Injections, Intravenous; D008970:Molecular Weight; D009206:Myocardium / Q000473:pathology / Q000648:ultrastructure; D032383:Myocytes, Cardiac / Q000166:cytology; D018995:Myosin Heavy Chains / Q000235:genetics; D018994:Myosin Light Chains / Q000235:genetics; D011401:Promoter Regions, Genetic; D020033:Protein Isoforms / Q000008:administration & dosage / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D016760:Proto-Oncogene Proteins c-fos / Q000235:genetics; D051381:Rats; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000511:alpha-Macroglobulins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*
D015415:Biomarkers; D018076:DNA, Complementary; D018994:Myosin Light Chains; D020033:Protein Isoforms; D016760:Proto-Oncogene Proteins c-fos; D000511:alpha-Macroglobulins; C107184:myosin light chain 2; D015500:Chloramphenicol O-Acetyltransferase; D024722:Cardiac Myosins; D018995:Myosin Heavy Chains