Abstract
Heat-shock protein (Hsp)10 is the co-chaperone for Hsp60 inside mitochondria, but it also resides outside the organelle. Variations in its levels and intracellular distribution have been documented in pathological conditions, e.g. cancer and chronic obstructive pulmonary disease (COPD). Here, we show that Hsp10 in COPD undergoes changes at the molecular and subcellular levels in bronchial cells from human specimens and derived cell lines, intact or subjected to stress induced by cigarette smoke extract (CSE). Noteworthy findings are: (i) Hsp10 occurred in nuclei of epithelial and lamina propria cells of bronchial mucosa from non-smokers and smokers; (ii) human bronchial epithelial (16HBE) and lung fibroblast (HFL-1) cells, in vitro, showed Hsp10 in the nucleus, before and after CSE exposure; (iii) CSE stimulation did not increase the levels of Hsp10 but did elicit qualitative changes as indicated by molecular weight and isoelectric point shifts; and (iv) Hsp10 nuclear levels increased after CSE stimulation in HFL-1, indicating cytosol to nucleus migration, and although Hsp10 did not bind DNA, it bound a DNA-associated protein.
Highlights
The 10 kDa heat-shock protein (Hsp10) is classically considered a mitochondrial co-chaperonin that interacts with Hsp60 to assist in the folding of other mitochondrial proteins [1]
We found that Hsp10 and Hsp60 decrease in bronchial dysplasia and adeno-squamous carcinoma [17,18], but increase in airways mucosa in smokers with chronic obstructive pulmonary disease (COPD) [19]
We found that Hsp10 and Hsp60 levels were increased in the bronchial epithelium of severe/very severe COPD compared with control non-smokers; by contrast, in lamina propria the number of Hsp10 positive cells was significantly increased in all stages of stable COPD compared with control smokers with normal lung function and nonsmoking subjects, while the number of Hsp60-positive cells was significantly higher only in severe/very severe COPD compared with control smokers with normal lung function
Summary
The 10 kDa heat-shock protein (Hsp10) is classically considered a mitochondrial co-chaperonin that interacts with Hsp to assist in the folding of other mitochondrial proteins [1]. Hsp does not contain a mitochondrial targeting sequence, but its translocation to the organelle is mediated by its N-terminal sequence that can form an amphipathic alpha helix, which enables it to cross the mitochondrial membrane [2,3]. Hsp has been found in extra-mitochondrial sites such as secretory granules from various cell types [4,5] and in circulation. License http://creativecommons.org/licenses/by/4.0/, which permits unrestricted use, provided the original author and source are credited. Hsp has been called early pregnancy factor (EPF) because it appears in the maternal serum within 24 h after fertilization in several mammalian species [6,7,8,9,10]
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