Morphological differentiation and proteoglycan synthesis regulate Alzheimer amyloid precursor protein processing in PC-12 and human astrocyte cultures.
A morphologically differentiated strain of rat pheochromocytoma (PC-12H) metabolically labeled with [35S]methionine and incubated with a phorbol ester displayed reduced 140-kDa and increased 15 kDa bands relative to cells incubated without phorbol ester after immunoprecipitation with antisera elicited by the C-terminal peptide of the Alzheimer amyloid precursor protein (APP). These bands correspond to glycosylated full length APP and a C-terminal fragment previously reported by Anderson et al. (Neurosci. Lett. 120:126-128, 1991) to result from a cleavage within the amyloidotic A4 region of APP, which releases a 120 kDa extracellular fragment. The 15 kDa fragment, not immunoprecipitated with an antisera elicited by the N-terminal portion of A4 amyloid, is nonamyloidogenic. Incubation of these cells with p-nitrophenylxyloside, known to inhibit proteoglycan formation, also increased this nonamyloidogenic cleavage of APP. In contrast to these results, an undifferentiated low passage PC-12-L strain constitutively displayed rapid nonamyloidogenic APP cleavage. Incubation of PC-12-L with phorbol ester did not affect the relative abundance of 140 or 15 kDa bands. Growth of PC-12-L with 7 S NGF or dibutyryl cAMP resulted in increased morphological differentiation and decreased APP cleavage which was now phorbol-inducible. Similar analyses of dividing and senescent human astrocytes and normal and F-AD fibroblasts indicate 5-fold lower rates of mid-A4 APP cleavage. Phorbol esters decreased the 140 kDa APP band without affecting the intensity of the 15 kDa band in these cells.(ABSTRACT TRUNCATED AT 250 WORDS)
Baskin
F
F
Department of Neurology, University of Texas Southwestern Medical Center, Dallas 75235-9036.
Rosenberg
R N
RN
Davis
R M
RM
D016564:Amyloid beta-Protein Precursor / Q000096:biosynthesis* / Q000276:immunology; D000818:Animals; D001253:Astrocytes / Q000378:metabolism*; D002454:Cell Differentiation / Q000502:physiology*; D006027:Glycosides / Q000494:pharmacology; D006801:Humans; D009447:Neuroblastoma / Q000378:metabolism; D016716:PC12 Cells; D010703:Phorbol Esters / Q000494:pharmacology; D011233:Precipitin Tests; D011509:Proteoglycans / Q000096:biosynthesis* / Q000276:immunology / Q000502:physiology; D014407:Tumor Cells, Cultured
D016564:Amyloid beta-Protein Precursor; D006027:Glycosides; D010703:Phorbol Esters; D011509:Proteoglycans; C008646:4-nitrophenyl beta-D-xyloside