The proteins of the nuclear lamina have generated enormous interest because of recent studies showing that mutations in the gene for lamin A/C (LMNA) develop a host of different diseases, including cardiomyopathy, muscular dystrophy, and partial lipodystrophy. The objectives of this proposal are to define the enzymes that are important in the posttranslational processing of the nuclear lamins and to understand the consequences of defective posttranslational processing at both the cellular and tissue levels. Prelamin A (664 amino acids) terminates with a """"""""CAAX"""""""" sequence motif and undergoes a complicated series of posttranslational modifications. First, the cysteine (C) of the CAAX motif is farnesylated by protein farnesyltransferase. Second, the last three amino acids of the protein (i.e., the -AAX) are released by a prenylprotein-specific endoprotease (likely Rce1 or Zmpste24 or both). Third, the newly exposed farnesylcysteine is methylated by isoprenylcysteine carboxyl methyltransferase (Icmt), a membrane protein of the endoplasmic reticulum. Fourth, once the cell has gone to all of this effort, the carboxyl-terminal 15 residues of the protein (including the farnesylcysteine methyl ester) are clipped off and degraded, leaving mature lamin A (646 amino acids). Zmpste24 might carry out that final endoproteolytic-processing step. Lamin B1 and B2 have a CAAX sequence motif and undergo the first three processing steps, but do not undergo a second endoproteolysis step; thus, their sequences terminate with a methylated farnesylcysteine. During the past few years, the laboratory of Dr. Stephen Young has generated knockout alleles [as well as some conditional (""""""""floxed"""""""") alleles] for many of the genes involved in CAAX protein processing (e.g., Fntb, Rce1, Zmpste24, and Icmt) for the purpose of analyzing the importance of the posttranslational processing steps. In mice lacking Zmpste24, the processing of prelamin A to lamin A was blocked. Of note, the Zmpste24-deficient mice exhibited reduced muscle strength (suggestive of a laminopathy), and also developed spontaneous bone fractures, a peculiar finding not generally observed in humans with lamin mutations.
The first aim of this grant application is to define, biochemically, the precise role(s) of Zmpste24 in prelamin A processing.
The second aim i s to further define the cellular and tissue pathology of Zmpste24 mice and then to determine whether all of the pathologic findings are due to defective prelamin A processing.
The third aim i s to understand the posttranslational processing of lamin B1 and to define the consequences of lamin B1 deficiency in mammals.

Agency
National Institute of Health (NIH)
Institute
National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS)
Type
Research Project (R01)
Project #
5R01AR050200-04
Application #
7079406
Study Section
Pathology A Study Section (PTHA)
Program Officer
Nuckolls, Glen H
Project Start
2003-09-15
Project End
2008-06-30
Budget Start
2005-07-01
Budget End
2006-06-30
Support Year
4
Fiscal Year
2005
Total Cost
$432,902
Indirect Cost
Name
University of California Los Angeles
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
092530369
City
Los Angeles
State
CA
Country
United States
Zip Code
90095
Coffinier, Catherine; Jung, Hea-Jin; Nobumori, Chika et al. (2011) Deficiencies in lamin B1 and lamin B2 cause neurodevelopmental defects and distinct nuclear shape abnormalities in neurons. Mol Biol Cell 22:4683-93
Liu, Meng; Sjogren, Anna-Karin M; Karlsson, Christin et al. (2010) Targeting the protein prenyltransferases efficiently reduces tumor development in mice with K-RAS-induced lung cancer. Proc Natl Acad Sci U S A 107:6471-6
Lee, Roger; Chang, Sandy Y; Trinh, Hung et al. (2010) Genetic studies on the functional relevance of the protein prenyltransferases in skin keratinocytes. Hum Mol Genet 19:1603-17
Coffinier, Catherine; Chang, Sandy Y; Nobumori, Chika et al. (2010) Abnormal development of the cerebral cortex and cerebellum in the setting of lamin B2 deficiency. Proc Natl Acad Sci U S A 107:5076-81
Yang, Shao H; Chang, Sandy Y; Andres, Douglas A et al. (2010) Assessing the efficacy of protein farnesyltransferase inhibitors in mouse models of progeria. J Lipid Res 51:400-5
Yang, Shao H; Bergo, Martin O; Farber, Emily et al. (2009) Caution! Analyze transcripts from conditional knockout alleles. Transgenic Res 18:483-9
Chan, Lai N; Hart, Courtenay; Guo, Lea et al. (2009) A novel approach to tag and identify geranylgeranylated proteins. Electrophoresis 30:3598-606
Fong, Loren G; Vickers, Timothy A; Farber, Emily A et al. (2009) Activating the synthesis of progerin, the mutant prelamin A in Hutchinson-Gilford progeria syndrome, with antisense oligonucleotides. Hum Mol Genet 18:2462-71
Davies, Brandon S J; Fong, Loren G; Yang, Shao H et al. (2009) The posttranslational processing of prelamin A and disease. Annu Rev Genomics Hum Genet 10:153-74
Worman, Howard J; Fong, Loren G; Muchir, Antoine et al. (2009) Laminopathies and the long strange trip from basic cell biology to therapy. J Clin Invest 119:1825-36

Showing the most recent 10 out of 42 publications