ABSTRACT
Over the past decade, the problem of calcium regulated exocytosis has become one of the most provocative and exciting areas of cell biology. Certainly, solving this problem would yield insight to fundamental mechanisms of neuroendocrine and exocrine secretion, with great impact for medicine. However, the subject has been of even broader interest because of the necessary interface with the general membrane fusion problem. This problem impacts on such diverse concerns as viral invasion, cell division, fertilization, mitochondrial replication, and many others. Although the requirement for Ca2+ in exocytosis has been known for nearly 40 years (summarized by Raynal and Pollard, 1994), the added requirement for other mediators such as GTP has only recently been realized. The purpose of this review is to focus attention on annexin VII as a mediator of both calcium and GTP on exocytotic membrane fusion, and to suggest that the mechanism of mastoparan toxin activation of secretion might also involve the annexin VII GTPase.
