Regulatory roles of fibronectin and integrin α5 in reorganization of the actin cytoskeleton and completion of adipogenesis.

Cellular differentiation is characterized by changes in cell morphology that are largely determined by actin dynamics. We previously showed that depolymerization of the actin cytoskeleton triggers the differentiation of preadipocytes into mature adipocytes as a result of inhibition of the transcriptional coactivator activity of megakaryoblastic leukemia 1 (MKL1). The extracellular matrix (ECM) influences cell morphology via interaction with integrins, and reorganization of the ECM is associated with cell differentiation. Here we show that interaction between actin dynamics and ECM rearrangement plays a key role in adipocyte differentiation. We found that depolymerization of the actin cytoskeleton precedes disruption and degradation of fibrillar fibronectin (FN) structures at the cell surface after the induction of adipogenesis in cultured preadipocytes. A FN matrix suppressed both reorganization of the actin cytoskeleton into the pattern characteristic of adipocytes and terminal adipocyte differentiation, and these inhibitory effects were overcome by knockdown of integrin α5 (ITGα5). Peroxisome proliferator-activated receptor γ was required for down-regulation of FN during adipocyte differentiation, and MKL1 was necessary for the expression of ITGα5. Our findings suggest that cell-autonomous down-regulation of FN-ITGα5 interaction contributes to reorganization of the actin cytoskeleton and completion of adipocyte differentiation.

Tubular-shaped nanocarbons prepared from polyaniline synthesized by a self-assembly process and their electrical conductivity.

A tubular-shaped polyaniline less than 5 microm in length and 170 nm in outer diameter was synthesized by a self-assembly process using D-camphorsulfonic acid as a dopant. A tubular-shaped nanocarbon was prepared from the tubular-shaped polyaniline by means of pyrolysis at 1000 degrees C in argon gas. The structural and electrical properties of the resultant tubular-shaped nanocarbons were investigated using Raman scattering spectrum, X-ray diffraction measurements, scanning and transmission electron microscopes, and a low resistivity meter. The tubular-shaped nanocarbons are very short in length and are an amorphous state. The short length and amorphous tubular-shaped nanocarbon were crystallized to some extent by heat-treatment at 2600 degrees C. The tubular-shaped nanocarbons mentioned in this work are appropriate for mass production, compared to the well-known multi-walled carbon nanotubes. The electrical conductively of the tubular-shaped polyaniline was remarkably improved by the carbonization and was enhanced by the heat-treatment.