The early induction of the actin-sequestering peptide thymosin beta 4 in thymocytes depends on the proliferative stimulus.
The expression of the actin-sequestering peptide, thymosin beta 4, was analyzed in proliferating rat thymocytes, activated by diverse stimuli, during the early G1 phase and the S phase. In the presence of concanavalin A a 6.3-fold increase of thymosin beta 4 occurred already after 1 h of stimulation without elevation of the corresponding mRNA level. In contrast, during the S phase the increase of thymosin beta 4 (2.5-fold) was accompanied by a higher mRNA level, but did not exceed the growth related increase of total protein. Stimulation with a crosslinked antibody against rat T cell antigen receptor or stimulation with phorbol 12-myristate 13-acetate (PMA) and Ca(2+)-ionophore A23187, separately or in combination, did not lead to the marked increase of the thymosin beta 4 concentration in the early G1 phase but resulted in elevated thymosin beta 4 peptide and mRNA levels during the S phase. It therefore appears that protein kinase C activation and a rise in cytoplasmic Ca(2+)-concentration are not exclusively responsible for the stimulation of thymosin beta 4 specific translation in thymocytes. This assumption was reinforced by the observation that inhibition of the protein kinase C activity by 1-(5-isoquinolinylsulfony)-2-methylpiperazine (H-7) did not affect the cellular thymosin beta 4 content 1 h and 48 h after concanavalin A (Con A) stimulation.
Schöbitz
B
B
Institute of Biochemistry, Medical Faculty, University of Erlangen-Nuremberg, Germany.
Hannappel
E
E
Brand
K
K
D000818:Animals; D000001:Calcimycin / Q000494:pharmacology; D002455:Cell Division; D003208:Concanavalin A / Q000494:pharmacology; D005260:Female; D015870:Gene Expression / Q000187:drug effects; D008840:Microfilament Proteins / Q000096:biosynthesis* / Q000235:genetics; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D047428:Protein Kinase Inhibitors; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D011919:Rats, Inbred Strains; D011948:Receptors, Antigen, T-Cell / Q000502:physiology; D011952:Receptors, Concanavalin A / Q000502:physiology; D015398:Signal Transduction; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013947:Thymosin / Q000031:analogs & derivatives* / Q000096:biosynthesis / Q000235:genetics; D013950:Thymus Gland / Q000378:metabolism*; D000099201:Thymosin beta(4)
D000001:Calcimycin; D003208:Concanavalin A; D008840:Microfilament Proteins; D011493:Protein Kinase C; D047428:Protein Kinase Inhibitors; D012333:RNA, Messenger; D011948:Receptors, Antigen, T-Cell; D011952:Receptors, Concanavalin A; D013755:Tetradecanoylphorbol Acetate; D013947:Thymosin; D000099201:Thymosin beta(4)