Antibodies to the C-terminus of the beta-amyloid precursor protein (APP): a site specific marker for the detection of traumatic axonal injury

Antibodies to the amyloid precursor protein (APP) are commonly used to dete ct traumatic axonal injury (TBI). Carried by fast anterograde axoplasmic tr ansport, APP will pool at regions of impaired transport associated with TAI . Based primarily upon commercial antibody availability, previous studies h ave targeted the N-terminus of APP, which, with respect to antigen detectio n, is suboptimally located within anterogradely transported vesicles. Recen tly, antibodies to the APP C-terminus, located on the external surface of a nterogradely transported vesicles, have become available, allowing for the exploration of their utility in detecting TAI. To this end, rats were subje cted to an impact acceleration injury, surviving 30 min to 24 h post-injury . They were then perfused, their brains sectioned and prepared for dual lab el immunofluorescent microscopy, single label bright field microscopy, and electron microscopy (EM). antibodies to the APP C-terminus yielded the read y detection of intensely labeled TAI with significantly reduced diffuse bac kground staining in comparison to antibodies to the APP N-terminus in both dual label immunofluorescent and single label bright-field approaches. EM e xamination of antibodies to the APP C-terminus in TAI revealed intense labe ling of pooled intra-axonal vesicular profiles, confirming the anterogradel y transported vesicular source of the APP seen in TAI. Interestingly, in ad dition to providing a technically superior approach and new detailed inform ation on the subcellular localization of APP, antibodies to the APP C-termi nus also proved more cost effective. Immunofluorescent studies of APP C-ter minus immunoreactivity involved 1/3 the cost of targeting the N-terminus, w hile bright field APP C-terminus studies were performed for 1/20 the cost. (C) 2000 Elsevier Science B.V. All rights reserved.