Myocardial alpha-thrombin receptor activation induces hypertrophy and increases atrial natriuretic factor gene expression.
The protease, alpha-thrombin (alpha Th), affects myocardial cell contractility, a feature common among agents that induce hypertrophy. However, it is not known whether cardiac myocytes possess alpha Th receptors (alpha Th-R), or if long term treatment with alpha Th can enhance growth and gene expression. In the present study primary neonatal rat ventricular myocytes expressed a 3.6-kilobase mRNA species that hybridized with a rat alpha Th-R-specific probe. After 48 h, alpha Th induced hypertrophy, sarcomeric organization, and enhanced atrial natriuretic factor (ANF) expression, all of which were blocked by the alpha Th-selective protease inhibitor, D-Phe-Pro-Arg-chloromethyl ketone. The alpha Th-R agonist peptide, SFLLRNPND, was a potent activator of ANF expression, however, the non-agonist, FLLRNPND, was inactive. Transfection experiments showed the enhancement of ANF expression by alpha Th to be transcriptional. The abilities of alpha Th to induce myocyte hypertrophy and to augment ANF transcription and peptide production were inhibited by the protein kinase C inhibitor, chelerythrine, and by the tyrosine kinase inhibitor, tyrphostin. Thus, myocardial cell alpha Th-Rs are stimulated by the specific proteolytic actions of alpha Th, and pathways involving both protein kinase C and protein tyrosine kinases are required for subsequent hypertrophy and ANF expression. Further, these findings suggest a new role for extracellular proteases as regulators of myocardial cell gene expression and growth.
Glembotski
C C
CC
Department of Biology, San Diego State University, California 92182.
Irons
C E
CE
Krown
K A
KA
Murray
S F
SF
Sprenkle
A B
AB
Sei
C A
CA
D000470:Alkaloids; D000595:Amino Acid Sequence; D000818:Animals; D000831:Animals, Newborn; D009320:Atrial Natriuretic Factor / Q000032:analysis / Q000096:biosynthesis*; D053119:Benzophenanthridines; D015152:Blotting, Northern; D006332:Cardiomegaly / Q000139:chemically induced / Q000473:pathology*; D002396:Catechols / Q000494:pharmacology; D002478:Cells, Cultured; D015870:Gene Expression / Q000187:drug effects*; D006352:Heart Ventricles; D007700:Kinetics; D008969:Molecular Sequence Data; D009206:Myocardium / Q000378:metabolism* / Q000473:pathology; D009570:Nitriles / Q000494:pharmacology; D009842:Oligopeptides / Q000138:chemical synthesis / Q000494:pharmacology*; D010617:Phenanthridines / Q000494:pharmacology; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology; D016133:Polymerase Chain Reaction / Q000379:methods; D011480:Protease Inhibitors / Q000138:chemical synthesis / Q000494:pharmacology*; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors; D012333:RNA, Messenger / Q000032:analysis / Q000096:biosynthesis*; D011863:Radioimmunoassay; D051381:Rats; D011956:Receptors, Cell Surface / Q000187:drug effects / Q000502:physiology*; D018179:Receptors, Thrombin; D013917:Thrombin / Q000494:pharmacology*; D020032:Tyrphostins
D000470:Alkaloids; D053119:Benzophenanthridines; D002396:Catechols; D009570:Nitriles; D009842:Oligopeptides; D010617:Phenanthridines; D010975:Platelet Aggregation Inhibitors; D011480:Protease Inhibitors; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; D018179:Receptors, Thrombin; D020032:Tyrphostins; C060152:tyrphostin 47; D009320:Atrial Natriuretic Factor; C016299:chelerythrine; D011505:Protein-Tyrosine Kinases; D013917:Thrombin