Decreased biosynthesis of actin and cellular fibronectin during adipose conversion of 3T3‐F442A cells. Reorganization of the cytoarchitecture and extracellular matrix fibronectin

Abstract

Differentiation of 3T3-F442A cells was accompanied by changes in cell morphology, decreased synthesis and assembly of actin and fibronectin. The network of microfilament stress fibers detected with NBD-phallacidin was altered during adipose conversion of 3T3-F442A cells. Parallel to this, the disappearance of fibrillar bundles of extracellular matrix fibronectin was observed by immunofluorescence staining. The pericellular fibronectin content, detected by immunoblotting, strongly diminished during the differentiation process. An altered rate of biosynthesis of both proteins was also measured by [35S]-methionine pulse-labeling and immunoprecipitation. A 4-5-fold decrease in cellular fibronectin synthesis was observed in adipocytes compared to control preadipocytes. Conversely, non-differentiating 3T3-C2 control cells did not reorganize either the cytoskeletal architecture or the extracellular matrix fibronectin in the resting state. These results suggest that the decreased rate of biosynthesis of cell-associated fibronectin is correlated with that of actin. Moreover, both events can essentially be ascribed to differentiation.

Influence of Extracellular Matrix on the Lipogenesis of Cultured White Fat Cells.

“…Similar results were reported using 3T3 cells [1,22]. It is interesting that cells on fibronectin have small amounts of cytoplasmic lipid droplets though covered with the secondary collagen layer.…”

“…Kuri-Harcuch et al pointed out that the differentiation of 3T3-F442A cells accompanied the production of ECM [14]. Antras et al [1] and Fernandez and Ben-Ze'ev [9] reported the inhibitory effect of fibronectin on the differentiation of 3T3-F442A cells.…”

Angiotensin-converting enzyme signalling in human preadipocytes and adipocytes

“…These results are in agreement with previously published mRNA data from human [23,24], but not rat adipose tissue [29]. As preadipocytes change the expression of classic "housekeepers" like actin during adipose conversion [30], γ-tubulin was therefore chosen as loading control. …”

Transcriptional repression of type I procollagen genes during adipocyte differentiation

“…However, less attention has focused on the modulations in cytoskeletal and ECM components accompanying adipocyte differentiation. During differentiation, expressions of actin, tubulin, fibronectin, type I and type III collagen, and pref-1 decrease whereas expressions of CSPG-1, entactin/nidogen, and type IV collagen increase (Spiegelman and Farmer, 1982;Aratani and Kitagawa, 1988;Antras et al, 1989;Weiner et al, 1989;Calvo et al, 1991;Smas and Sul, 1993). Among these, collagen is the major ECM protein and shown to drastically decrease in mRNA level by 80-90% during 3T3-L1 differentiation (Weiner et al, 1989).…”

“…Besides significant increases in mRNAs of the genes directly involved in lipidogenesis, changes occur in expression of cytoskeletal, extracellular matrix (ECM), and related components such as actin, tubulin, fibronectin, and collagen (Spiegelman and Farmer, 1982;Antras et al, 1989;Weiner et al, 1989). Modulation of cytoskeletal and ECM components could allow for cytoskeletal rearrangement, release of cell adhesion, and remodeling of cell components necessary for morphological changes.…”