Differential effects of the phosphatidylinositol 4-kinases, PI4KIIα and PI4KIIIβ, on Akt activation and apoptosis

In this study, we investigated the role of PI4P synthesis by the phosphatidylinositol 4-kinases, PI4KIIα and PI4KIIIβ, in epidermal growth factor (EGF)-stimulated phosphoinositide signaling and cell survival. In COS-7 cells, knockdown of either isozyme by RNA interference reduced basal levels of PI4P and PI(4,5)P2, without affecting receptor activation. Only knockdown of PI4KIIα inhibited EGF-stimulated Akt phosphorylation, indicating that decreased PI(4,5)P2 synthesis observed by loss of either isoform could not account for this PI4KIIα-specific effect. Phospholipase Cγ activation was also differentially affected by knockdown of either PI4K isozyme. Overexpression of kinase-inactive PI4KIIα, which induces defective endosomal trafficking without reducing PI(4,5)P2 levels, also reduced Akt activation. Furthermore, PI4KIIα knockdown profoundly inhibited cell proliferation and induced apoptosis as evidenced by the cleavage of caspase-3 and its substrate poly(ADP-ribose) polymerase. However, in MDA-MB-231 breast cancer cells, apoptosis was observed subsequent to knockdown of either PI4KIIα or PI4KIIIβ and this correlated with enhanced proapoptotic Akt phosphorylation. The differential effects of phosphatidylinositol 4-kinase knockdown in the two cell lines lead to the conclusion that phosphoinositide turnover is inhibited through PI4P substrate depletion, whereas impaired antiapoptotic Akt signaling is an indirect consequence of dysfunctional endosomal trafficking

A Picture is Worth a Thousand Words: Practical Use of Videotape in Teaching

Videotapes, through vividly displayed clinical images and teaching interactions, are valuable tools for both learners and teachers. Visual images in combination with verbal instruction have been shown to significantly increase recall and retention. Many clinicians and medical teachers are aware of videotape resources, but have not had a chance to develop their use in medical education. In this paper, we discuss creative applications of videotapes in three major categories: presenting information, triggering discussion, and as a tool for direct self-observation and feedback. Videotapes may be valuable for presenting information in settings of didactic instruction; for triggering discussion during teaching workshops; and for self-observation of patient-doctor interactions and learner-teacher encounters. The article presents learner-centered approaches to review a videotaped clinical encounter in order to enhance value and comfort for the learner and teacher. Sources of tapes include on-site videotaping, published educational tapes and commercial tapes shown in accordance with fair use guidelines, examples of which are referenced. Videotapes add another dimension to traditional sources of physician education