A proteomic-informed view of the changes induced by loss of cellular adherence: The example of mouse macrophages

Abstract

Except cells circulating in the bloodstream, most cells in vertebrates are adherent. Studying the repercussions of adherence per se in cell physiology is thus very difficult to carry out, although it plays an important role in cancer biology, e.g. in the metastasis process. In order to study how adherence impacts major cell functions, we used a murine macrophage cell line. Opposite to the monocyte/macrophage system, where adherence is associated with the acquisition of differentiated functions, these cells can be grown in both adherent or suspension conditions without altering their differentiated functions (phagocytosis and inflammation signaling). We used a proteomic approach to cover a large panel of proteins potentially modified by the adherence status. Targeted experiments were carried out to validate the proteomic results, e.g. on metabolic enzymes, mitochondrial and cytoskeletal proteins. The mitochondrial activity was increased in non-adherent cells compared with adherent cells, without differences in glucose consumption. Concerning the cytoskeleton, a rearrangement of the actin organization (filopodia vs sub-cortical network) and of the microtubule network were observed between adherent and non-adherent cells. Taken together, these data show the mechanisms at play for the modification of the cytoskeleton and also modifications of the metabolic activity between adherent and non-adherent cells.

Morphological Evidence for Novel Roles of Microtubules in Macrophage Phagocytosis

“…Since we have previously compared and examined fixation protocols for clear visualization of microtubules in another experimental system [ 27 , 28 ], we could improve the fixation and staining protocols. In some previous studies from other groups, although the authors did not mention the microtubule networks, there are clear photographs showing the microtubule network in macrophages, similar to our results [ 29 , 30 ]. Analyses of macrophages using innovative imaging technologies are becoming increasingly important for a precise understanding of immunology.…”