Modulation of GJA1 Turnover and Intercellular Communication by Proinflammatory Cytokines in the Anterior Pituitary Folliculostellate Cell Line TtT/GF1

Abstract

Our previous studies have advanced the idea that the folliculostellate cell GJA1 (gap junction membrane channel protein alpha1; previously known as connexin 43)-mediated gap junctions contribute to the establishment of an intercellular network that regulates the paracrine messages and the endocrine response within the anterior pituitary. The folliculostellate cells are targets for growth factors and cytokines that modulate hormone secretion. Proinflammatory cytokines modulate the cell-to-cell communication in many tissues of the body. The present study measured the effect of the proinflammatory cytokines tumor necrosis factor and interleukin-1 on the GJA1-mediated intercellular communication, specifically the expression, localization, degradation, and phosphorylation status of GJA1 in the folliculostellate cell line TtT/GF. The GJA1 localized to the plasma membrane and to minute cytoplasmic vesicles in the perinuclear area. Using different antibodies that recognize distinctly the nonphosphorylated from the phosphorylated forms of GJA1, we showed that nonphosphorylated GJA1 in Ser-368 (NP-GJA1) localized chiefly in the cytoplasm, whereas GJA1 phosphorylated in Ser-368 (P-GJA1) localized to the plasma membrane in controls. The cytokine treatment transiently increased 1) GJA1, NP-GJA1, and P-GJA1 levels; 2) NP-GJA1 and P-GJA1 degradation by both the lysosomal and proteasomal pathways; and 3) cell-to-cell communication in TtT/GF cells. The results suggest that the cytokine-evoked, transient enhancement of folliculostellate cell-mediated intercellular communication contributes to the coordination of the response among folliculostellate cells.

Actin cytoskeleton remodelling in the anterior pituitary folliculostellate cell line TtT/GF: participation of the actin-binding protein cortactin

“…It is more difficult for cellto-cell interactions to develop in fibroblast-like cells, likely because these cells tend to be isolated and to interact with the extracellular matrix rather than with other cells. Nevertheless, we found that although TtT/GF cells express the gap junction protein connexin 43, there is very little expression of tight and adherens junction proteins (Fortin et al 2006). During serum starvation, TtT/GF cells acquired a polygonal shape and they are closer to one another.…”

Isoform B of myosin II heavy chain mediates actomyosin contractility during TNFα-induced apoptosis

“…The study used the folliculostellate (FS) cell line TtT/GF, a stable mouse cell line characterised by morphological and biochemical features of normal FS cells (Allaerts and Vankelecom, 2005;Inoue et al, 1992). TtT/GF cells express the TNFR1 receptor (Kobayashi et al, 1997) and are responsive to TNFα (Fortin et al, 2006;Kobayashi et al, 1997;Meilleur et al, 2007). Here, we report a distinctive participation of MHCIIA and MHCIIB in the execution phase of apoptosis.…”

Folliculo-stellate Cells: Paracrine Communicators in the Anterior Pituitary

“…TtT/GF cells [125,127] Lipopolysaccharide (LPS) IL-6 production TtT/GF cells [117] Mouse pituitary [128] Macrophage inhibitory factor (MIF) production…”