Differential effects of thin and thick filament disruption on zebrafish smooth muscle regulatory proteins.
BACKGROUND
The smooth muscle actin binding proteins Caldesmon and Tropomyosin (Tm) promote thin filament assembly by stabilizing actin polymerization, however, whether filament assembly affects either the stability or activation of these and other smooth muscle regulatory proteins is not known.


METHODS
Measurement of smooth muscle regulatory protein levels in wild type zebrafish larvae following antisense knockdown of smooth muscle actin (Acta2) and myosin heavy chain (Myh11) proteins, and in colourless mutants that lack enteric nerves. Comparison of intestinal peristalsis in wild type and colourless larvae.


RESULTS
Knockdown of Acta2 led to reduced levels of phospho-Caldesmon and Tm. Total Caldesmon and phospho-myosin light chain (p-Mlc) levels were unaffected. Knockdown of Myh11 had no effect on the levels of either of these proteins. Phospho-Caldesmon and p-Mlc levels were markedly reduced in colourless mutants that have intestinal motility comparable with wild type larvae.


CONCLUSIONS
These in vivo findings provide new information regarding the activation and stability of smooth muscle regulatory proteins in zebrafish larvae and their role in intestinal peristalsis in this model organism.
Davuluri
G
G
Department of Medicine, University of Pennsylvania School of Medicine, Philadelphia, PA, USA.
Seiler
C
C
Abrams
J
J
Soriano
A J
AJ
Pack
M
M
D008841:Actin Cytoskeleton / Q000502:physiology*; D000818:Animals; D002148:Calmodulin-Binding Proteins / Q000096:biosynthesis / Q000235:genetics; D017615:Enteric Nervous System / Q000502:physiology; D007150:Immunohistochemistry; D007413:Intestinal Mucosa / Q000378:metabolism; D007422:Intestines / Q000166:cytology* / Q000502:physiology*; D007814:Larva; D008840:Microfilament Proteins / Q000378:metabolism; D018613:Microscopy, Confocal; D009025:Morpholines / Q000494:pharmacology; D009124:Muscle Proteins / Q000378:metabolism*; D009130:Muscle, Smooth / Q000166:cytology* / Q000378:metabolism / Q000502:physiology*; D009154:Mutation / Q000502:physiology; D018995:Myosin Heavy Chains / Q000096:biosynthesis / Q000235:genetics; D018994:Myosin Light Chains / Q000096:biosynthesis / Q000235:genetics; D010528:Peristalsis / Q000502:physiology; D016372:RNA, Antisense; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D014335:Tropomyosin / Q000096:biosynthesis / Q000235:genetics; D015027:Zebrafish / Q000502:physiology*; D029961:Zebrafish Proteins / Q000378:metabolism*
D002148:Calmodulin-Binding Proteins; D008840:Microfilament Proteins; D009025:Morpholines; D009124:Muscle Proteins; D018994:Myosin Light Chains; D016372:RNA, Antisense; D012333:RNA, Messenger; D014335:Tropomyosin; D029961:Zebrafish Proteins; D018995:Myosin Heavy Chains