TOPOGRAPHIC VARIABILITIES OF IMMUNOREACTIVITY TO SUBUNIT-C OF MITOCHONDRIAL ATP SYNTHASE AND LECTIN-BINDING IN LATE INFANTILE NEURONAL CEROID-LIPOFUSCINOSIS

A subset of lipophilic neurons in the brain tissue of late infantile n euronal ceroid lipofuscinosis (LINCL) cases shows in addition to finel y granular storage lipopigment, larger spheroidal lysosomal inclusions , so called protein-type myoclonus bodies. Their incidence, significan ce, and biochemical composition have not been determined. To further c haracterize this type of lysosomal storage material, immunocytochemist ry to subunit c of mitochondrial ATP synthase at the light and electro n microscopy level, electron microscopy, and lectin histochemistry wer e applied. The majority of spheroidal inclusions were nonreactive to s ubunit c, the main protein component of the storage material in LINCL. These inclusions also showed no binding sites for the eight lectins e xamined, although six of the lectins used labeled finely granular stor age material. According to electron and immunoelectron microscopy, sph eroidal inclusions were composed of more homogeneous and more densely arranged material than typical curvilinear profiles, with shorter memb ranous profiles and sometimes filamentous structures. The dissimilarit ies disclosed between finely granular lipopigment with curvilinear pro files and spheroidal inclusions in LINCL brain tissue suggest that eit her protein(s) other than subunit c are present in spheroidal inclusio ns, or subunit c in these sites undergoes conformational or proteolyti c changes. These changes require further biochemical evaluations. (C) 1995 Wiley-Liss, Inc.