Beclin-1 Deficiency Alters Autophagosome Formation, Lysosome Biogenesis and Enhances Neuronal Vulnerability of HT22 Hippocampal Cells.

Beclin-1 is assumed to be a critical component participating in autophagosome formation in mammals; however, the exact role of Beclin-1 in autophagy remains controversial. Here (1) we created a HT22-Beclin-1-knockdown cell line using the Q- techBECN1 technique, (2) examined the potential role of Beclin-1 in an autophagic response in hippocampal HT22 neurons challenged with rapamycin, (3) investigated the expression of several gene products involved in the autophagic pathway, and (4) checked the effects of Beclin-1 knockdown on neuronal death induced by AAS. Rapamycin induced and altered the expression of autophagy signature proteins in wild-type cultures as well as in HT22-Beclin-1-knockdown cells. However, among the examined markers, only two factors exhibited dramatic changes when comparing controls to HT22-Beclin-1-knockdown cells. The amount of LC3, an important protein for the initiation of autophagosome formation and LAMP-1, a major constituent of the lysosomal membrane, underwent a dramatic and highly significant increase in control cultures challenged with rapamycin. In contrast, rapamycin was not able to induce any significant changes in LC3 and LAMP-1 levels in HT22-Beclin-1-knockdown cells. In addition, the knockdown of Beclin-1 enhanced neuronal susceptibility to death signals induced by AAS. Our data demonstrate the essential role of Beclin-1 in the formation of autophagosomes and lysosome biogenesis and underline that deletion of this key system is deleterious for cell viability. [ABSTRACT FROM AUTHOR]