Fibronectin Peptides Derived from Two Distinct Regions Stimulate Adipocyte Differentiation by Preventing Fibronectin Matrix Assembly

Abstract

Here, we show that fibronectin (FN) peptides derived from two distinct regions promote the insulin-induced adipocyte differentiation of ST-13 cells by preventing FN fibrillogenesis. ST-13 cells formed numerous FN fibrils under nonadipogenic conditions, whereas this FN fibrillogenesis was suppressed by adipose induction with insulin. The insulin-induced adipocyte differentiation was promoted by an amino-terminal 24-kDa fragment of FN, accompanied by further suppression of FN fibrillogenesis. The 24 K fragment prevented FN matrix assembly by direct incorporation into the FN matrix. Like the 24 K fragment, a peptide from the 14th type III repeat, termed FNIII14, which suppressed the integrin alpha 5 beta 1-mediated adhesion of ST-13 cells to FN, accelerated the adipocyte differentiation by preventing FN fibrillogenesis without direct incorporation into the FN matrix. FNIII14 induced the conformation change of beta1 integrins of K562 cells from active to resting, as judged by FACS analysis using a monoclonal antibody AG89 directed to an active beta1 integrin-dependent epitope. Binding of a (125)I-labeled FN fragment containing the RGD cell adhesive site to ST-13 cell surface was dissociated by FNIII14, with a concomitant binding of FNIII14 itself to the cell surface. The affinity labeling of ST-13 cells using biotinylated FNIII14 showed that FNIII14 specifically bound to a nonintegrin membrane protein with M(r) of around 50 kDa. Thus, the results indicated that prevention of FN fibrillogenesis by the 24 K Fib 1 fragment and FNIII14 caused the promotion of adipocyte differentiation of ST-13 cells and that the former was due to the direct incorporation into the FN matrix and that the latter might be interpreted by negative regulation of FN receptor alpha 5 beta 1 activity.

Combination therapy of an anticancer drug with the FNIII14 peptide of fibronectin effectively overcomes cell adhesion-mediated drug resistance of acute myelogenous leukemia

“…23 It was also shown that FNIII14 clearly prevented murine T-lymphoma cell metastasis. 21 Since peptide preparation is generally less expensive than humanizing antibody, it may be worthy to study FNIII14 in eradication of MRD in terms of cost/benefit for clinical use.…”

Coculture of Endothelial Cells and Mature Adipocytes Actively Promotes Immature Preadipocyte Development In Vitro.

“…In addition, this phenomenon was observed around the contact sites between the mature adipocytes and endothelial RLE cells. Recently, fibronectin is reported to play a crucial role in the biological behavior of adipocytes (Kamiya et al, 2002). Thus, adhesion-related molecules that mediate cell-cell interaction seem to be critical in the differentiation and/or dedifferentiation of adipocytes.…”

Inhibition of Angiogenesis by a Tenascin-C Peptide which Is Capable of Activating Beta1-Integrins

“…2A). FNIII14, an FN peptide opposing b1-integrin activation, 12) had no significant effect on HDMEC migration by itself (data not shown), but was capable of restoring HDMEC migration when used in combi-nation with TNIIIA2 (Fig. 2B).…”

“…b1-Integrin activation by TNIIIA2 was reversed ( Fig. 1E) when FNIII14, an antiadhesive peptide derived from FN, that has the ability to inactivate b1-integrins (see above), 12) was used in combination with TNIIIA2. Thus, TNIIIA2 was demonstrated to induce activation of b1-integrins on HDMEC.…”

“…10) FNIII14, a 22-mer FN peptide that contains this active site, inhibits cell adhesion to the ECM by inactivating b1-integrins. 11,12) Interestingly, tenascin (TN)-C, which is an antiadhesive ECM protein, has a cryptic functional site that stimulates cell adhesion to the ECM. 13) A 22-mer TN-C peptide containing this cryptic site, termed TNIIIA2, positively regulates b1-integrin-mediated cell adhesion to the ECM by inducing a conformational change in b1-integrins, which is necessary for their functional activation.…”