Limits...
Keratin 8 overexpression promotes mouse Mallory body formation.

Nakamichi I, Toivola DM, Strnad P, Michie SA, Oshima RG, Baribault H, Omary MB - J. Cell Biol. (2005)

Bottom Line: Early stages in MB genesis include K8/18 hyperphosphorylation and overexpression.MBs were induced by feeding 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC).Thus, the K8 to K18 ratio, rather than K8/18 overexpression by itself, plays an essential role in MB formation.

View Article: PubMed Central - PubMed

Affiliation: Department of Medicine, Stanford University, and Veterans Affairs Palo Alto Health Care System, CA 94305, USA.

ABSTRACT
Keratins 8 and 18 (K8/18) are major constituents of Mallory bodies (MBs), which are hepatocyte cytoplasmic inclusions seen in several liver diseases. K18- but not K8- or heterozygous mice form MBs, which indicates that K8 is important for MB formation. Early stages in MB genesis include K8/18 hyperphosphorylation and overexpression. We used transgenic mice that overexpress K8, K18, or K8/18 to test the importance of K8 and/or K18 in MB formation. MBs were induced by feeding 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC). Livers of young K8 or K8/K18 overexpressors had no histological abnormalities despite increased keratin protein and phosphorylation. In aging mice, only K8-overexpressing livers spontaneously developed small "pre-MB" aggregates. Only K8-overexpressing young mice are highly susceptible to MB formation after short-term DDC feeding. Thus, the K8 to K18 ratio, rather than K8/18 overexpression by itself, plays an essential role in MB formation. K8 overexpression is sufficient to form pre-MB and primes animals to accumulate MBs upon DDC challenge, which may help explain MB formation in human liver diseases.

Show MeSH

Related in: MedlinePlus

Spontaneous pre-MB formation in livers of old K8 mice. Immunofluorescence staining was performed on livers of 2-yr-old WT, K8, K18, and K8/18 mice. Livers were stained with Abs to K8/18 (pankeratin; A, C, E, and G) or to K18 pS33 (B, D, F, and H). Arrows (C and D) highlight keratin aggregates that are seen only in K8-overexpressing mice, whereas the asterisks highlight fine keratin dots that are likely precursors to the larger aggregates. Bar, 50 μm. Insets show double staining of K8/18 (C) and ubiquitin (D) and illustrate that the larger keratin aggregates are ubiquitin positive (arrowheads), whereas the smaller keratin dots are ubiquitin negative (asterisks).
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2171301&req=5

fig2: Spontaneous pre-MB formation in livers of old K8 mice. Immunofluorescence staining was performed on livers of 2-yr-old WT, K8, K18, and K8/18 mice. Livers were stained with Abs to K8/18 (pankeratin; A, C, E, and G) or to K18 pS33 (B, D, F, and H). Arrows (C and D) highlight keratin aggregates that are seen only in K8-overexpressing mice, whereas the asterisks highlight fine keratin dots that are likely precursors to the larger aggregates. Bar, 50 μm. Insets show double staining of K8/18 (C) and ubiquitin (D) and illustrate that the larger keratin aggregates are ubiquitin positive (arrowheads), whereas the smaller keratin dots are ubiquitin negative (asterisks).

Mentions: Given that MBs form spontaneously in old but not in young K18- mice (Magin et al., 1998), we asked whether keratin deposits form in old mouse livers isolated from WT, K8, K18, and K8/18 mice. Notably, livers from 2-yr-old K8 mice develop keratin aggregates of varied sizes, whereas livers of similarly aged WT, K18, or K8/18 mice do not (Fig. 2). The keratin aggregates consist of small dots located primarily near the cell periphery and of larger, MB-like cytoplasmic aggregates, which also stained positive for K18 pS33 (Fig. 2, C and D) even though clear MB formation was not seen by histochemical staining (not depicted). The larger keratin-containing aggregates uniformly included ubiquitin, whereas the smaller dots did not (Fig. 2, C and D; insets). Some hepatocytes from K8/18 mice had brighter keratin staining, but keratin aggregates were rarely found (Fig. 2, G and H). The K8 aggregates excluded γ-tubulin and, thus, were not related to centrosomes nor to apoptosis, as they did not stain with an Ab specific to an apoptotic K18 fragment, and most did not colocalize with autophagosomes (Fig. S2, available at http://www.jcb.org/cgi/content/full/jcb.200507093/DC1). Altogether, we hypothesize that the keratin aggregates noted in the K8-overexpressing old mice represent pre-MBs as defined by the formation of K8/18-ubiquitin aggregates that are not easily seen by histochemical staining.


Keratin 8 overexpression promotes mouse Mallory body formation.

Nakamichi I, Toivola DM, Strnad P, Michie SA, Oshima RG, Baribault H, Omary MB - J. Cell Biol. (2005)

Spontaneous pre-MB formation in livers of old K8 mice. Immunofluorescence staining was performed on livers of 2-yr-old WT, K8, K18, and K8/18 mice. Livers were stained with Abs to K8/18 (pankeratin; A, C, E, and G) or to K18 pS33 (B, D, F, and H). Arrows (C and D) highlight keratin aggregates that are seen only in K8-overexpressing mice, whereas the asterisks highlight fine keratin dots that are likely precursors to the larger aggregates. Bar, 50 μm. Insets show double staining of K8/18 (C) and ubiquitin (D) and illustrate that the larger keratin aggregates are ubiquitin positive (arrowheads), whereas the smaller keratin dots are ubiquitin negative (asterisks).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2171301&req=5

fig2: Spontaneous pre-MB formation in livers of old K8 mice. Immunofluorescence staining was performed on livers of 2-yr-old WT, K8, K18, and K8/18 mice. Livers were stained with Abs to K8/18 (pankeratin; A, C, E, and G) or to K18 pS33 (B, D, F, and H). Arrows (C and D) highlight keratin aggregates that are seen only in K8-overexpressing mice, whereas the asterisks highlight fine keratin dots that are likely precursors to the larger aggregates. Bar, 50 μm. Insets show double staining of K8/18 (C) and ubiquitin (D) and illustrate that the larger keratin aggregates are ubiquitin positive (arrowheads), whereas the smaller keratin dots are ubiquitin negative (asterisks).
Mentions: Given that MBs form spontaneously in old but not in young K18- mice (Magin et al., 1998), we asked whether keratin deposits form in old mouse livers isolated from WT, K8, K18, and K8/18 mice. Notably, livers from 2-yr-old K8 mice develop keratin aggregates of varied sizes, whereas livers of similarly aged WT, K18, or K8/18 mice do not (Fig. 2). The keratin aggregates consist of small dots located primarily near the cell periphery and of larger, MB-like cytoplasmic aggregates, which also stained positive for K18 pS33 (Fig. 2, C and D) even though clear MB formation was not seen by histochemical staining (not depicted). The larger keratin-containing aggregates uniformly included ubiquitin, whereas the smaller dots did not (Fig. 2, C and D; insets). Some hepatocytes from K8/18 mice had brighter keratin staining, but keratin aggregates were rarely found (Fig. 2, G and H). The K8 aggregates excluded γ-tubulin and, thus, were not related to centrosomes nor to apoptosis, as they did not stain with an Ab specific to an apoptotic K18 fragment, and most did not colocalize with autophagosomes (Fig. S2, available at http://www.jcb.org/cgi/content/full/jcb.200507093/DC1). Altogether, we hypothesize that the keratin aggregates noted in the K8-overexpressing old mice represent pre-MBs as defined by the formation of K8/18-ubiquitin aggregates that are not easily seen by histochemical staining.

Bottom Line: Early stages in MB genesis include K8/18 hyperphosphorylation and overexpression.MBs were induced by feeding 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC).Thus, the K8 to K18 ratio, rather than K8/18 overexpression by itself, plays an essential role in MB formation.

View Article: PubMed Central - PubMed

Affiliation: Department of Medicine, Stanford University, and Veterans Affairs Palo Alto Health Care System, CA 94305, USA.

ABSTRACT
Keratins 8 and 18 (K8/18) are major constituents of Mallory bodies (MBs), which are hepatocyte cytoplasmic inclusions seen in several liver diseases. K18- but not K8- or heterozygous mice form MBs, which indicates that K8 is important for MB formation. Early stages in MB genesis include K8/18 hyperphosphorylation and overexpression. We used transgenic mice that overexpress K8, K18, or K8/18 to test the importance of K8 and/or K18 in MB formation. MBs were induced by feeding 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC). Livers of young K8 or K8/K18 overexpressors had no histological abnormalities despite increased keratin protein and phosphorylation. In aging mice, only K8-overexpressing livers spontaneously developed small "pre-MB" aggregates. Only K8-overexpressing young mice are highly susceptible to MB formation after short-term DDC feeding. Thus, the K8 to K18 ratio, rather than K8/18 overexpression by itself, plays an essential role in MB formation. K8 overexpression is sufficient to form pre-MB and primes animals to accumulate MBs upon DDC challenge, which may help explain MB formation in human liver diseases.

Show MeSH
Related in: MedlinePlus