LOCALIZATION OF SPECIFIC EPITOPES ON HUMAN MICROTUBULE-ASSOCIATED PROTEIN-2

Microtubule-associated protein 2 (MAP-2) is an abundant neuronal cytos keletal protein that binds to tubulin and stabilizes microtubules. Usi ng fusion protein constructs we have defined the epitopes of 10 monocl onal antibodies (mAbs) to discrete regions of human MAP-2. Proteins we re expressed in pATH vectors. After electrophoresis, immunoblotting wa s performed. By western blot analysis five of the mAbs (AP-14, AP-20, AP-21, AP-23, and AP-25) share epitopes with only the high molecular w eight isoforms (MAP-2a, MAP-2b); two of the mAbs (AP-18 and tau 46) re cognize MAP-2a, MAP-2b, and MAP-2c. Although AP-18 immunoreactivity wa s detected within heat-stable protein homogenates isolated from a huma n neuroblastoma cell line MSN, fusion protein constructs encompassing human MAP-2 were negative, suggesting that the AP-18 epitope is phosph orylated. Furthermore, AP-18 immunoreactivity was lost after alkaline phosphatase treatment of heat-stable protein preparations from MSN cel ls. Four of the mAbs (322, 636, 635, and 39) recognize epitopes locate d within amino acids 169-219 of human MAP-2. AP-21 maps to a region be tween amino acids 553 and 645. AP-23 maps between amino acids 645 and 993, whereas AP-20, AP-14, and AP-25 map between amino acids 995 and 1 332. Expression of the region of MAP-2 between amino acids 1787 and 18 24 was positive to tau 46.