AXONAL-TRANSPORT AND DISTRIBUTION OF CYCLOPHILIN-A IN CHICKEN NEURONS

In the course of pulse-label studies on the axonal transport of the sm all, basic, actin-binding proteins - actin depolymerizing factor, cofi lin and profilin - in chicken motor neurones, we observed a heavily la belled protein of M-r 18 kDa and pI 8.2 on fluorographs of two-dimensi onal polyacrylamide gels. On the basis of its M-r, pI and amino acid c omposition, we tentatively identified it by database searching as cycl ophilin A and subsequently confirmed its identity by immunostaining. L ike actin and its associated proteins, cyclophilin A was transported i n slow component b of axonal transport, but unlike these proteins, cyc lophilin A did not copurify with actin on DNase I. It was not found am ongst labelled proteins transported by fast axonal transport. Immunost aining of chicken dorsal root ganglion cells revealed that it accumula ted in neurites at points of branching, varicosities and growth cones. Our results raise the possibility that cyclophilin A is important in maintaining the native folding of actin and associated proteins during transit in axons and assembly in growth cones. (C) 1997 Elsevier Scie nce B.V.