title: Less than 5 Netrin-1 molecules initiate attraction but 200 Sema3A molecules are necessary for repulsion.
abstract: Guidance molecules, such as Sema3A or Netrin-1, induce growth cone (GC) repulsion or attraction. In order to determine the speed of action and efficiency of these guidance cues we developed an experimental procedure to deliver controlled amounts of these molecules. Lipid vesicles encapsulating 10-10(4) molecules of Sema3A or Netrin-1 were manipulated with high spatial and temporal resolution by optical tweezers and their photolysis triggered by laser pulses. Guidance molecules released from the vesicles diffused and reached the GC membrane in a few seconds. Following their arrival, GCs retracted or grew in 20-120 s. By determining the number of guidance molecules trapped inside vesicles and estimating the fraction of guidance molecules reaching the GC, we show that the arrival of less than 5 Netrin-1 molecules on the GC membrane is sufficient to induce growth. In contrast, the arrival of about 200 Sema3A molecules is necessary to induce filopodia repulsion.
authors.affiliation: Istituto Officina dei Materiali (IOM-CNR), Area Science Park, Trieste, Italy. pinato@iom.cnr.it
authors.forename: Giulietta
authors.initials: G
authors.lastname: Pinato
authors.forename: Dan
authors.initials: D
authors.lastname: Cojoc
authors.forename: Linh Thuy
authors.initials: LT
authors.lastname: Lien
authors.forename: Alessio
authors.initials: A
authors.lastname: Ansuini
authors.forename: Jelena
authors.initials: J
authors.lastname: Ban
authors.forename: Elisa
authors.initials: E
authors.lastname: D'Este
authors.forename: Vincent
authors.initials: V
authors.lastname: Torre
mesh_terms: D000465:Algorithms; D000818:Animals; D002465:Cell Movement; D002478:Cells, Cultured; D000075389:DCC Receptor; D020439:Growth Cones / Q000502:physiology*; D006624:Hippocampus / Q000166:cytology; D008954:Models, Biological; D009414:Nerve Growth Factors / Q000502:physiology*; D000075386:Netrin Receptors; D000075388:Netrin-1; D009474:Neurons / Q000378:metabolism / Q000502:physiology*; D039942:Neuropilin-1 / Q000378:metabolism; D011554:Pseudopodia / Q000378:metabolism / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D011956:Receptors, Cell Surface / Q000378:metabolism; D040121:Semaphorin-3A / Q000502:physiology*; D018709:Statistics, Nonparametric; D025521:Tumor Suppressor Proteins / Q000378:metabolism / Q000502:physiology*
chemical_list: D000075389:DCC Receptor; C501912:Dcc protein, rat; D009414:Nerve Growth Factors; D000075386:Netrin Receptors; C000617354:Ntn1 protein, rat; D011956:Receptors, Cell Surface; C488218:Sema3a protein, rat; D040121:Semaphorin-3A; D025521:Tumor Suppressor Proteins; D039942:Neuropilin-1; D000075388:Netrin-1