A-type lamins regulate retinoblastoma protein function by promoting subnuclear localization and preventing proteasomal degradation

Johnson, Brett; Nitta, Ryan T.; Frock, Richard L.; Mounkes, Leslie C.; Barbie, David A.; Stewart, Colin L.; Harlow, Ed; Kennedy, Brian K.

doi:10.1073/pnas.0403250101

Cited by 252 publications

(271 citation statements)

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“…We have demonstrated that pRB stability, but not proper subnuclear localization, could be restored to Lmna Ϫ/Ϫ fibroblasts by prolonged treatment with the proteasome inhibitor MG132 (27). Here, we extend these studies by testing the kinetics of pRB degradation in the absence of A-type lamins.…”

Section: Resultsmentioning

confidence: 68%

“…2A). In the Lmna Ϫ/Ϫ cells 70% of the 3xFlag-pRB was degraded by 2 h, whereas only 10% was degraded in the Lmna ϩ/ϩ fibroblasts after 6 h. Addition of MG132 blocked the degradation of pRB levels in the presence of cycloheximide, confirming that pRB degradation in the absence of Atype lamins is proteasome dependent (27).…”

Section: Resultsmentioning

confidence: 76%

“…Previous studies have shown that lamin A/C and pRB interact in vitro, leading to speculation that the nuclear structural component regulates pRB activity (41,42,51). We have reported that immortalized mouse Lmna Ϫ/Ϫ fibroblasts have fivefold reduced pRB levels (27). To test the generality of this observation, we used siRNA methodology to reduce the expression of lamin A/C in NIH 3T3 cells (siLmna cells, see Materials and Methods).…”

Section: Resultsmentioning

confidence: 98%

“…Since Lmna Ϫ/Ϫ fibroblasts have lower steady-state pRB levels, we speculated that the extent of pRB ubiquitination may be increased in these cells (27). Therefore, we cotransfected 3xFlag-pRB and HA-Ub into Lmna Ϫ/Ϫ fibroblasts and Lmna ϩ/ϩ littermate control cells and performed coimmunoprecipitation experiments (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…Previously, it has been shown that pRB is tethered to the nuclear substructure through the action of lamin A/C (66). Further, A-type lamins protect pRB, and the related protein p107, from proteasomal degradation (27). pRB regulates cell cycle progression by inhibiting the activity of the transcriptional activator E2F and through establishment of repressive chromatin structures at genes necessary for S-phase entry and progression (2,4,16,22).…”

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confidence: 99%

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Stabilization of the Retinoblastoma Protein by A-Type Nuclear Lamins Is Required for INK4A-Mediated Cell Cycle Arrest

Nitta¹,

Jameson²,

Kudlow

et al. 2006

Molecular and Cellular Biology

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Mutations in the LMNA gene, which encodes all A-type lamins, including lamin A and lamin C, cause a variety of tissue-specific degenerative diseases termed laminopathies. Little is known about the pathogenesis of these disorders. Previous studies have indicated that A-type lamins interact with the retinoblastoma protein (pRB). Here we probe the functional consequences of this association and further examine links between nuclear structure and cell cycle control. Since pRB is required for cell cycle arrest by p16 ink4a , we tested the responsiveness of multiple lamin A/C-depleted cell lines to overexpression of this CDK inhibitor and tumor suppressor. We find that the loss of A-type lamin expression results in marked destabilization of pRB. This reduction in pRB renders cells resistant to p16 ink4a -mediated G 1 arrest. Reintroduction of lamin A, lamin C, or pRB restores p16 ink4a -responsiveness to Lmna ؊/؊ cells. An array of lamin A mutants, representing a variety of pathologies as well as lamin A processing mutants, was introduced into Lmna ؊/؊ cells. Of these, a mutant associated with mandibuloacral dysplasia (MAD R527H), as well as two lamin A processing mutants, but not other disease-associated mutants, failed to restore p16 ink4a responsiveness. Although our findings do not rule out links between altered pRB function and laminopathies, they fail to support such an assertion. These findings do link lamin A/C to the functional activation of a critical tumor suppressor pathway and further the possibility that somatic mutations in LMNA contribute to tumor progression.A-type lamins are intermediate filament proteins that have been linked to the organization and maintenance of nuclear structure. In most differentiated tissues, A-type lamins (predominantly lamins A and C), along with lamin B, comprise the meshwork underlying the inner nuclear membrane known as the nuclear lamina (63). Unlike lamin C, lamin A contains a carboxy-terminal CaaX motif and must undergo a series of posttranslational modifications to form the mature lamin A (77). In particular, the cysteine of the CaaX motif in lamin A is isoprenylated, followed by cleavage of the aaX and carboxymethylation of the C-terminal cysteine (72). Lastly, a second cleavage event by Zmpste24 removes the last 15 amino acids to yield the mature lamin A (3, 13, 74).Mutations within the LMNA gene cause a variety of human disorders collectively known as laminopathies. These include progeria syndromes and dystrophies associated with skeletal muscle and adipose tissue (5,10,15,19,45,58). Mice lacking A-type lamins or deficient in processing lamin A develop skeletal and cardiac muscular dystrophies, thus confirming the importance of A-type lamins for muscle differentiation and/or maintenance (52, 65). The mechanism by which mutations in A-type lamins generate tissue-specific disorders is unknown. However, one model posits that lamin A/C regulates gene expression in differentiated tissue by coordinating the activity of key transcription factors.A-type lamins localize to p...

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Section: Resultsmentioning

confidence: 68%

Section: Resultsmentioning

confidence: 76%

Section: Resultsmentioning

confidence: 98%

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

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Stabilization of the Retinoblastoma Protein by A-Type Nuclear Lamins Is Required for INK4A-Mediated Cell Cycle Arrest

Nitta¹,

Jameson²,

Kudlow

et al. 2006

Molecular and Cellular Biology

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Cellular Basis of Laminopathies

Cao

2012

Encyclopedia of Life Sciences

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The nuclear lamina is the main architectural component of a eukaryotic nucleus. More than an inert scaffold, the lamina is essential for maintaining proper nuclear organisation, epigenetic composition, transcriptional regulation and cell cycle progression. Mutations within lamin genes lead to a wide range of diseases known as laminopathies, among which the striking premature aging disease Hutchinson–Gilford progeria syndrome (HGPS) is the most well known. Studies regarding the cellular basis of laminopathies have advanced our knowledge of the nuclear lamina and yielded remarkable insights into the process of normal human aging. Understanding the molecular mechanisms responsible for disease manifestations has also led to the development of novel therapeutic strategies to address lamina‐related diseases. Ultimately, scientists and clinicians seek to provide treatment options to laminopathy patients to alleviate symptoms and perhaps to cure these diseases in the future. Key Concepts: Mutations in genes encoding lamin proteins lead to a wide range of diseases known as laminopathies. The nuclear lamina plays essential roles in maintaining nuclear architecture, chromatin organisation, cellular differentiation and gene expression. Studies of the molecular mechanisms underlying laminopathies have led to advances in the understanding of lamin structure and function. Progerin, the mutant form of lamin A expressed in Hutchinson–Gilford progeria syndrome, is also present in normal individuals, albeit at a low level. Recent advances have led to the development of noval therapeutic options for patients suffering from HGPS.

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The Retinoblastoma Tumour Suppressor

Dirlam¹,

Macleod²

2007

The Cancer Handbook

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The retinoblastoma tumour suppressor (pRB) is functionally inactivated in most human cancers. pRB regulates cell cycle checkpoints, cell death, cellular senescence, and terminal differentiation through interactions with members of the E2F family of transcription factors, chromatin‐remodelling factors and with tissue‐restricted transcription factors. The RB‐related “pocket proteins”, p107 and p130 also interact with E2Fs to regulate cell cycle, although neither p107 nor p130 are known tumour suppressors in human cancer, despite data from mouse models indicating their ability to compensate for Rb loss under certain circumstances. This chapter discusses the latest findings on the role of pRB in development and tumourigenesis to help determine which functions of pRB contribute most to its tumour‐suppressor activity, why certain tumours select against RB but others do not, and what kind of additional mutations are likely to cooperate with RB loss in cancer as a function of tissue type.

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A-type lamins regulate retinoblastoma protein function by promoting subnuclear localization and preventing proteasomal degradation

Cited by 252 publications

References 39 publications

Stabilization of the Retinoblastoma Protein by A-Type Nuclear Lamins Is Required for INK4A-Mediated Cell Cycle Arrest

Stabilization of the Retinoblastoma Protein by A-Type Nuclear Lamins Is Required for INK4A-Mediated Cell Cycle Arrest

Cellular Basis of Laminopathies

The Retinoblastoma Tumour Suppressor

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