Nebulin 

nebulin
Identifiers
Symbol NEB
Alt. Symbols NEM2
Entrez 4703
HUGO 7720
OMIM 161650
RefSeq NM_004543
UniProt P20929
Other data
Locus Chr. 2 q22

Nebulin is an actin-binding protein which is localized to the I-band the sarcomeres in skeletal muscle. It is a very large protein (600-900 kDa) and binds as many as 200 actin monomers. Because its length is proportional to thin filament length, it is believed that nebulin acts as a thin filament "ruler" and regulates thin filament length during sarcomere assembly.1 Other functions of nebulin, such as a role in cell signaling, remain uncertain.

The interaction of nebulin with actin is calcium-calmodulin sensitive.2

Mutations in nebulin cause some cases of the autosomal recessive disorder nemaline myopathy.3

A second smaller isoform of nebulin, termed nebulette, is expressed in cardiac muscle.

Knockout phenotype

As of 2007, two knockout mouse models for nebulin have been developed to better understand its in vivo function. Bang and colleagues4 demonstrated that nebulin-knockout mice die postnatally, have reduced thin filament length, and impaired contractile function. Postnatal sarcomere disorganization and degeneration occurred rapidly in these mice, indicating the nebulin is essential for maintaining the structural integrity of myofibrils. Witt and colleagues5 had similar results in their mice, which also died postnatally with reduced thin filament length and contractile function. These nebulin-knockout mice are being investigated as animal models of nemaline myopathy.

References

  1. ^ McElhinny et al (2003). "Nebulin: the nebulous, multifunctional giant of striated muscle". Trends Cardiovasc Med 13 (5): 195–201. doi:10.1016/S1050-1738(03)00076-8. PMID 12837582. 
  2. ^ Root & Wang (1994). "Calmodulin-sensitive interaction of human nebulin fragments with actin and myosin". Biochemistry 33 (42): 12581–91. doi:10.1021/bi00208a008. PMID 7918483. 
  3. ^ Pelin et al (1999). "Mutations in the nebulin gene associated with autosomal recessive nemaline myopathy". Proc Natl Acad Sci USA 96 (5): 2305–10. doi:10.1073/pnas.96.5.2305. PMID 10051637. 
  4. ^ Bang et al (2006). "Nebulin-deficient mice exhibit shorter thin filament lengths and reduced contractile function in skeletal muscle". J Cell Biol 173 (6): 905–16. doi:10.1083/jcb.200603119. PMID 16769824. 
  5. ^ Witt et al (2006). "Nebulin regulates thin filament length, contractility, and Z-disk structure in vivo". EMBO J 25 (16): 3843–55. doi:10.1038/sj.emboj.7601242. PMID 16902413. 

External links

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Histology: muscle tissue
skeletal muscle/general
cardiac muscle
smooth muscle