Microtubule-associated protein-4 (MAP-4) inhibits microtubule-dependent distribution of mRNA in isolated neonatal cardiocytes.
OBJECTIVE
Active mRNA distribution in the form of ribonucleoprotein particles moving along microtubules has been shown in several cell types, but not yet in cardiocytes. This study addresses two hypotheses: 1) a similar mRNA distribution mechanism operates in cardiocytes; 2) decoration of microtubules with microtubule-associated proteins compromises this distribution.


METHODS
To visualize ribonucleoproteins in cultured neonatal rat cardiocytes, they were transfected with vectors encoding zipcode binding protein-1 and Staufen fused with GFP. The velocity of microtubular transport and elongation were calculated on time-lapse confocal pictures.


RESULTS
ZBP-1 and Staufen labeled particles co-localized with each other and with microtubules and moved along microtubules over a distance of 1-20 microm with a mean speed of 80 nm/s. The average speed decreased about 50% after decoration of microtubules by adenoviral microtubule-associated protein-4 (MAP-4). The elongation speed measured using the GFP-tagged end-binding protein-1 exceeded 200 nm/s and was not influenced by MAP-4.


CONCLUSIONS
We demonstrate for the first time ribonucleoprotein particles in cardiocytes, their microtubular-related movement, and its inhibition (but not of the microtubular elongation), by the MAP-4 decoration of microtubules.
Scholz
Dimitri
D
Gazes Cardiac Research Institute, Cardiology Division, Medical University of South Carolina, and Department of Veterans Affairs Medical Center, Charleston, SC 29401, United States. scholzd@musc.edu
McDermott
Paul
P
Garnovskaya
Maria
M
Gallien
Thomas N
TN
Huettelmaier
Stefan
S
DeRienzo
Christina
C
Cooper
George
G
D000818:Animals; D000831:Animals, Newborn; D001692:Biological Transport / Q000502:physiology; D002478:Cells, Cultured; D018613:Microscopy, Confocal; D008869:Microtubule-Associated Proteins / Q000502:physiology*; D008870:Microtubules / Q000378:metabolism*; D032383:Myocytes, Cardiac / Q000378:metabolism* / Q000648:ultrastructure; D012333:RNA, Messenger / Q000378:metabolism*; D051381:Rats; D012261:Ribonucleoproteins / Q000378:metabolism; D014162:Transfection
D008869:Microtubule-Associated Proteins; D012333:RNA, Messenger; D012261:Ribonucleoproteins