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© The Rockefeller University Press,
0021-9525/1999//1287 $5.00
The Journal of Cell Biology, Volume 147, Number 6,
, 1999 1287-1298
Original Article |
Vertebrate Isoforms of Actin Capping Protein β Have Distinct Functions in Vivo
jcooper{at}cellbio.wustl.edu
Actin capping protein (CP) binds barbed ends of actin filaments to regulate actin assembly. CP is an
Mice expressing β2 had a severe phenotype with juvenile lethality. Myofibril architecture was severely disrupted. The β2 did not localize to the Z-line. Therefore, β1 has a distinct function that includes interactions at the Z-line. Mice expressing β1 showed altered morphology of the intercalated disc, without the lethality or myofibril disruption of the β2-expressing mice.
The in vivo function of CP is presumed to involve binding barbed ends of actin filaments. To test this hypothesis, we expressed a β1 mutant that poorly binds actin. These mice showed both myofibril disruption and intercalated disc remodeling, as predicted.
Therefore, CPβ1 and CPβ2 each have a distinct function that cannot be provided by the other isoform. CPβ1 attaches actin filaments to the Z-line, and CPβ2 organizes the actin at the intercalated discs.
/β heterodimer. Vertebrates have conserved isoforms of each subunit. Muscle cells contain two β isoforms. β1 is at the Z-line; β2 is at the intercalated disc and cell periphery in general. To investigate the functions of the isoforms, we replaced one isoform with another using expression in hearts of transgenic mice.
Key Words: isoform • heart • cardiomyopathy • Z line • sarcomere
© 1999 The Rockefeller University Press
Abbreviations used in this paper:-MyHC, -myosin heavy chain; CP, capping protein.
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