A mechanism generating heterogeneity in thyroid epithelial cells: suppression of the thyrotropin/cAMP-dependent mitogenic pathway after cell division induced by cAMP-independent factors

Abstract

. The mechanisms that generate the intercellular heterogeneity of functional and proliferation responses in a tissue are generally unknown . In the thyroid gland, this heterogeneity is peculiarly marked and it has been proposed that it could result from the coexistence of genetically different subpopulations of thyrocytes. To evaluate the heterogeneity of proliferative responses in primary culture of dog thyrocytes, we asked whether the progeny of cells having incorporated 1H thymidine in a first period of the culture could have a distinct proliferative fate during a second labeling period (incorporation of bromodeoxyuridine revealed by immunofluorescence staining combined with autoradiography of 3H thymidine) . No growth-prone subpopulations were detected and the great majority of cells were found to response to either EGF or thyrotropin (TSH) through cAMP. However, only a fraction of cells replicated DNA at one given period and a clustered distribution of labeled cells within the monolayer, which was different for thymidine-or bromodeoxyuridine-labeled cells, indicates some local and temporal

The CDK4/CDK6 inhibitor PD0332991 paradoxically stabilizes activated cyclin D3-CDK4/6 complexes

“…DNA replicating cells were identified by a 30 min incubation with BrdU. 65 CHO cells were transfected for 48 h using JetPEI (Polyplus Transfection) with 6 mg of pcDNA3 vector encoding myc-tagged CDK4 and Xpress-cyclin D3, and 6 mg of PE vector encoding p21. 15 …”

Signal transduction in the human thyrocyte and its perversion in thyroid tumors

“…In dog thyrocytes, the proliferation in response to serum or growth factors specifically extincts their capacity to respond to TSH/cAMP as a mitogenic stimulus (Roger et al, 1992). Similarly, in less differentiated thyroid cancers generated by the subversion of growth factor mechanisms, the TSH-dependence of growth is generally found to be lost, and in various cell lines derived from thyroid carcinomas, cAMP and PKA activation even inhibit CDK4 activity and cell cycle progression (Rocha et al, 2008).…”

Characterization of a Phosphoprotein whose mRNA is Regulated by the Mitogenic Pathways in Dog Thyroid Cells

“…After washing, cells were incubated for 2 h with a Texas-red-linked antibody (from donkey) raised against rabbit immunoglobulin (Amersham Corp., 1/50 in NaCl/P,/BSA). Fluorescent cells were mounted, visualized and photographed as described [23] using fluorescent microscopy (Zeiss).…”