ALTERATIONS OF GENE EXPRESSION INDUCED BY TEMPERATURE AND THYROID HORMONE IN AMPHIBIAN CELL CULTURES.

摘要

Primary epidermal cell cultures from wholly larval (tail fin) and adult (hind limb) organs were incubated briefly at temperatures between 22 and 36.5(DEGREES)C. At 32, 34 and 36.5(DEGREES)C, epidermal cell cultures from tail fin and hind limb depressed the synthesis of 'control' proteins and synthesized a novel heat shock protein (HSP) of 65 kd (pI 6.7-6.8); synthesis of an additional HSP (M(,r) = 25 kd) was detected only at 36.5(DEGREES)C. The synthesis of these HSPs is transient as control protein synthesis is virtually restored 4 hr after returning the cultures to the control (22(DEGREES)C) temperature. The results indicate that these cells respond to fluctuations in temperature by the depressed synthesis of proteins normally made at 22(DEGREES)C and the non-coordinate synthesis of HSPs.;The presence of T(,3) in the culture medium did not induce changes in the water-insoluble proteins synthesized by primary tail fin epidermal cell cultures after 36 hr or 5 days. This suggests that longer exposure to, or greater concentration of T(,3) may be required to elicit a differentiative (in this case, degenerative) effect on these cell cultures. Alternatively, T(,3) may not induce any changes in the water-insoluble proteins synthesized by tissues destined for degeneration.;Treatment of R. catesbeiana in situ with T(,3) (3 x 10('-10) moles/gram body weight) demonstrates that the water-insoluble proteins synthesized by hind limb epidermal cells from T(,3)-treated and control larvae are the same but differ from those induced by T(,3) in cultured epidermal cells. The discrepancy may be due to (1) an initial dedifferentiation making cultured cells more responsive to T(,3) or (2) the effects of T(,3) may be more evident in the absence of tissue-tissue interactions.;The effect of T(,3) on the water-insoluble proteins synthesized by epidermal cell cultures was examined. Hind limb epidermal cell cultures maintained in the presence of T(,3) (3 x 10('-10) moles/mL) for 36 hours synthesized water-insoluble proteins which corresponded closely in M(,r) and pI to keratins typical of epidermal differentiation. Many of these water-insoluble proteins are precipitable with rabbit anti-human cytokeratin antibodies. This suggests that T(,3) promotes a precocious induction of certain water-insoluble proteins in hind limb epidermal cell cultures that have immunochemical properties similar to mammalian keratins.