Decreased cyclin-dependent kinase activity promotes thyroid hormone-dependent tail regression in Rana catesbeiana

Abstract

The thyroid hormone (TH), 3,5,3'-triiodothyronine (T(3)), is an important regulator of diverse cellular processes including cell proliferation, differentiation, and apoptosis, with increasing evidence that the modulation of the phosphoproteome is an important factor in the TH-mediated response. However, little is understood regarding the mechanisms whereby phosphorylation may contribute to T(3)-mediated cellular outcomes during development. The cyclin-dependent kinases (Cdks) and mitogen-activated protein kinases (MAPK/ERK) have been implicated in TH signaling in mammalian cells. In this study, we have investigated, in frogs, the possible role that these kinases may have in the promotion of tail regression during tadpole metamorphosis, an important postembryonic process that is completely TH-dependent. Cdk2 steady state levels and activity increase in the tail concurrent with progression through the growth phase of metamorphosis, followed by a precipitous decrease coinciding with tail regression. Cyclin-A-associated kinase activity also follows a similar trend except that its associated kinase activity is maintained longer before a decrease in activity. Protein steady state levels of ERK1 and ERK2 remain relatively constant, and their kinase activities do not decrease until much later during tail regression. Tail tips cultured in serum-free medium in the presence of T(3) undergo regression, which is accelerated by coincubation with a specific Cdk2 inhibitor. Coincubation with PD098059, a MAPK inhibitor, has no effect. Thus, T(3)-dependent tail regression does not require MAPKs, but a decrease in Cdk2 activity promotes tail regression.

Influence of temperature on thyroid hormone signaling and endocrine disruptor action in Rana (Lithobates) catesbeiana tadpoles

“…These include additional transcription regulators, transporters, proteases, structural proteins, and metabolic enzymes involved in cell proliferation, apoptotic events, and tissue remodeling (Brown et al, 1996;Das et al, 2006;Helbing et al, 2003;Searcy et al, 2012;Skirrow and Helbing, 2007). In a biphasic metamorphic process under temperature regulation, such effectors would be expected to display attenuated response to TH at low temperature conditions.…”

C‐fin: A cultured frog tadpole tail fin biopsy approach for detection of thyroid hormone‐disrupting chemicals

“…Biopsies were cultured in individual wells at 25°C in air for 48 h in 24‐well multi‐well culture plates (Primaria, BD Biosciences) in 1 ml per biopsy of 70% strength Leibovitz's L15 medium (Gibco, Invitrogen) supplemented with 10 mM HEPES pH 7.5, 50 units/ml penicillin G sodium, 50 µg/ml streptomycin sulfate (Gibco, Invitrogen) and 50 µg/ml neomycin (Sigma‐Aldrich) 9, 17, 18. T 3 was prepared as a 10 −5 M stock in 400 µM NaOH and was applied at 1 µl/ml of media, giving a final concentration of 10 nM T 3 (25 nM NaOH final).…”

“…Preparation of the tail fin biopsy cultures was adapted from conditions described previously [9,17,18]. Premetamorphic (Taylor and Kollros [TK] stage VI-VIII [16]) R. catesbeiana tadpoles were euthanized in 0.1% tricaine methanesulfonate (Syndel Laboratories) in 25 mM sodium bicarbonate, and subsequently washed three times in 100 ml per tadpole of sterile magnesium-free (MFM) solution (7.5 mM Tris-HCl pH 7.6, 88 mM NaCl, 1 mM KCl, 2.4 mM NaHCO 3 , 0.88 mM CaCl 2 ).…”

Apoptosis in amphibian organs during metamorphosis

“…Inhibition of cyclin-dependent-kinase (Cdk) 2, whose expression is down-regulated during metamorphic climax, accelerates TH-induced tail regression [109]. In contrast, inhibition of protein kinase C prevents TH-induced tail regression [110].…”