Intermediate filaments and steroidogenesis in adrenal Y-1 cells: acrylamide stimulation of steroid production.

Abstract

The possible role of intermediate filaments in steroidogenesis was investigated in Y-1 mouse adrenal tumor cells by treatment with acrylamide, which is thought to disrupt intermediate filaments without directly affecting microtubules or microfilaments. Treatment of cells with 5 mM acrylamide increases steroidogenesis after a lag period of 4-6 h and induces rounding of the cells at approximately the same time. The effect of acrylamide on steroidogenesis is not cAMP mediated and occurs before pregnenolone formation. DNA synthesis is inhibited, while protein synthesis is not. Acrylamide does not affect polymerization/depolymerization of microtubules in vitro. Acrylamide stimulation of steroidogenesis is additive with that produced by either colchicine or ACTH, implying that acrylamide, ACTH, and colchicine act at different rate-limiting steps in steroidogenesis. In addition, acrylamide stimulation is additive with that of forskolin. Pretreatment of cells with taxol, an agent that specifically promotes microtubule polymerization, decreases acrylamide-stimulated (as well as colchicine or ACTH-stimulated) steroidogenesis, implying that there must also be some shared elements in the stimulating pathways. We hypothesize that regulation of steroidogenesis in the Y-1 cell depends on 1) disruption of a vimentin or tubulin coat surrounding lipid droplets and 2) possible functional shortening of the distance between cholesterol droplets and the mitochondrion. However, because of interactions between cytoplasmic fibers, it is currently impossible to say whether interruption of any one of them is a direct or indirect stimulus of steroidogenesis.

Dephosphorylation of MAP2D enhances its binding to vimentin in preovulatory ovarian granulosa cells

“…8A). Intermediate filament destabilization resulted in characteristic cell rounding but had no apparent effect on microtubule stability, in agreement with observations of others (Kumar et al, 2007;Shiver et al, 1992). We then tested whether treatment of granulosa cells with IDPN modulated progesterone secretion into the culture medium by cells treated with or without hCG for 5 h. Results (Fig.…”

“…Finally, vimentin disassembly is believed to be necessary for cholesterol trafficking to mitochondria (reviewed in Hall and Almahbobi, 1997). Consistent with this hypothesis, chemical disruption of vimentin filaments increases steroidogenesis in adrenal cells (Lee and Mrotek, 1984;Shiver et al, 1992). Our results showing enhanced progesterone release from granulosa cells in response to the vimentin-filamentdisrupting agent IDPN are consistent with the notion that cholesterol mobilization is facilitated by disruption of the vimentin intermediate filament network.…”

“…Moreover, the genetic ablation of vimentin resulted in a 70% decrease in hCG-stimulated progesterone production, compared to wild-type mice, by preovulatory granulosa cells (Shen et al, 2012), although the mice remain fertile (Colucci-Guyon et al, 1994). Trophic hormones, through PKA (Rae et al, 1979), promote mobilization of free cholesterol from intracellular lipid droplets to the outer mitochondrial membrane (Liscum and Munn, 1999) by a series of events that appear to include the disassembly of vimentin filaments (Hall and Almahbobi, 1997;Lee and Mrotek, 1984;Shiver et al, 1992).…”

Effects of acrylamide, latrunculin, and nocodazole on intracellular transport and cytoskeletal organization in melanophores

“…The third major component of the cytoskeleton, intermediate filaments, has no established role in melanosome transport [Gyoeva et al, 1987]. However, based on the finding that both microtubules and actin filaments were strongly affected by ACR, and the fact that intermediate filaments are potential targets of ACR [Eckert, 1985;Sager and Matheson, 1988;Sager, 1989;Shiver et al, 1992], we looked at the effects of ACR also on vimentin filaments. To our knowledge, vimentin filaments have not previously been visualized in Xenopus melanophores.…”

Interdependence of steroidogenesis and shape changes in Y1 adrenocortical cells: studies with inhibitors of phosphoprotein phosphatases

“…This change precedes the steroidogenic response and it has been suggested that the reorganisation of the actin skeleton that occurs facilitates delivery of cholesterol to the outer mitochondrial membrane thus leading to increased steroid synthesis (Betz & Hall 1987, Shiver et al 1992, Feuilloley & Vaudry 1996, Hall 1997. Recently, it has been demonstrated that an early effect of PKA activation is targeted to the protein paxillin, a component of focal adhesions which is dephosphorylated on tyrosine residues within minutes of exposure of Y1 cells and bovine adrenocortical cells to cyclic AMP (Han & Rubin 1996, Vilgrain et al 1998.…”