title: Microtubule-associated protein-4 (MAP-4) inhibits microtubule-dependent distribution of mRNA in isolated neonatal cardiocytes.
abstract: 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.
authors.affiliation: 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
authors.forename: Dimitri
authors.initials: D
authors.lastname: Scholz
authors.forename: Paul
authors.initials: P
authors.lastname: McDermott
authors.forename: Maria
authors.initials: M
authors.lastname: Garnovskaya
authors.forename: Thomas N
authors.initials: TN
authors.lastname: Gallien
authors.forename: Stefan
authors.initials: S
authors.lastname: Huettelmaier
authors.forename: Christina
authors.initials: C
authors.lastname: DeRienzo
authors.forename: George
authors.initials: G
authors.lastname: Cooper
mesh_terms: 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
chemical_list: D008869:Microtubule-Associated Proteins; D012333:RNA, Messenger; D012261:Ribonucleoproteins