Nestin Promotes the Phosphorylation-dependent Disassembly of Vimentin Intermediate Filaments During Mitosis

The expression of the intermediate filament (IF) protein nestin is closely associated with rapidly proliferating progenitor cells during neurogenesis and myogenesis, but little is known about its function. In this study, we examine the effects of nestin expression on the assembly state of vimentin IFs in nestin-free cells. Nestin is introduced by transient transfection and is positively correlated with the disassembly of vimentin IFs into nonfilamentous aggregates or particles in mitotic but not interphase cells. This nestin-mediated disassembly of IFs is dependent on the phosphorylation of vimentin by the maturation/M-phase–promoting factor at ser-55 in the amino-terminal head domain. In addition, the disassembly of vimentin IFs during mitosis appears to be a unique feature of nestin-expressing cell types. Furthermore, when the expression of nestin is downregulated by the nestin-specific small interfering RNA in nestin-expressing cells, vimentin IFs remain assembled throughout all stages of mitosis. Previous studies suggest that nonfilamentous vimentin particles are IF precursors and can be transported rapidly between different cytoplasmic compartments along microtubule tracks. On the basis of these observations, we speculate that nestin may play a role in the trafficking and distribution of IF proteins and potentially other cellular factors to daughter cells during progenitor cell division

The hypoxia-sensor carbonic anhydrase IX affects macrophage metabolism, but is not a suitable biomarker for human cardiovascular disease

Hypoxia is prevalent in atherosclerotic plaques, promoting plaque aggravation and subsequent cardiovascular disease (CVD). Transmembrane protein carbonic anhydrase IX (CAIX) is hypoxia-induced and can be shed into the circulation as soluble CAIX (sCAIX). As plaque macrophages are hypoxic, we hypothesized a role for CAIX in macrophage function, and as biomarker of hypoxic plaque burden and CVD. As tumor patients with probable CVD are treated with CAIX inhibitors, this study will shed light on their safety profile. CAIX co-localized with macrophages (CD68) and hypoxia (pimonidazole), and correlated with lipid core size and pro-inflammatory iNOS+ macrophages in unstable human carotid artery plaques. Although elevated pH and reduced lactate levels in culture medium of CAIX knock-out (CAIXko) macrophages confirmed its role as pH-regulator, only spare respiratory capacity of CAIXko macrophages was reduced. Proliferation, apoptosis, lipid uptake and expression of pro- and anti-inflammatory genes were not altered. Plasma sCAIX levels and plaque-resident CAIX were below the detection threshold in 50 and 90% of asymptomatic and symptomatic cases, respectively, while detectable levels did not associate with primary or secondary events, or intraplaque hemorrhage. Initial findings show that CAIX deficiency interferes with macrophage metabolism. Despite a correlation with inflammatory macrophages, plaque-resident and sCAIX expression levels are too low to serve as biomarkers of future CVD.publishedVersionPeer reviewe