Synaptic differentiation can be evoked by polymer microbeads that mimic localized pericellular proteolysis by removing proteins from adjacent surfaces☆

摘要

Synapticdifferentiationisnormallya€?induceda€?byregulatorysignalsthatareexchangedonlyatclosecontactsbetweenneuritesandtheirpredeterminedtargetcells.Thesesignalscan,however,bemimickedbycontactofeithercellwithsomekindsofpolymermicrobeads.Tofindwhatbeadactionisresponsibleforthismimicry,wecomparedtheeffectsofactiveandinertmicrobeadsonXenopusmusclecellsdevelopingincultureandonglass-adsorbedfilmsoflamininorfibronectin.Ourresultsshowthatinductivebioactivityisapropertyofnativepolystyrenemicrobeadsthat(a)isnotdependentmerelyonbead-muscleadhesion,(b)canbeeliminatedsimplybyexposingthebeadstoinertserumproteins,and(c)correlatescloselywiththeabilityofsomebeadstodesorbproteinsfromadjacentsurfaces.Quasi-synapticdifferentiationofthemusclesurfacethusseemstobetriggeredbythefocalremovalofperipheralcellsurfacecomponents,ratherthanbydirectbeadinteractionswithmembranereceptorsorionchannelsortheirgradualacquisitionofendogenousregulatorysubstances.Sincenerve-muscleinteractionalsocausesaneliminationofextracellularmatrixproteinsfromthemusclesurface,veryearlyinsynapsedevelopment,weconsiderthepossibilitythattheextracellulardegradationofperipheralsurfacecomponentscontributestothetransmissionofinductivepositionalsignalsduringsynaptogenesis.