CELLULAR HIGHWAYS - These vesicles are bags of cargo transported along microtubules inside living cells by tiny walking machines. New work from the Straube lab shows how KIF1C, one type of walking machine, is folded up and kept inactive when not loaded with cargo. PTPN21 and Hook3 are two activators that unfold KIF1C, allow it to engage with microtubules and start walking, dragging their cargo vesicles along.