Sperm acrosome biogenesis and function during fertilization

BUFFONE MG

Springer-VERLAG BERLIN

Lugar: Frankfurt; Año: 2016 p. 172

978-3-319-30567-7

Since its discovery in 1952, acrosomal exocytosis (also called acrosome reaction) has been a fascinating process that captured the attention of many researchers. For many years, acrosomal exocytosis was thought as a carriage of proteases. However, several discoveries along the last 64 years have produced a shifted in the operational view of the acrosome, from the earlier ?large lysosome? model to more complex model where the acrosome possess a central role in the process of fertilization. Although acrosomal exocytosis share many features with other exocytotic processes, it also has unique properties and its occurrence is limited to the male gamete, resulting in an ideal target for developing new drugs for male contraception. However, up to now, no acrosome-specific proteins whose inhibition would block this process have been discovered as occurred with other sperm functions (i.e. CatSper channel and hyperactivation, Izumo1 and sperm egg-fusion; Slo3 and membrane hyperpolarization).Despite that a few years after its discovery, it was noticed that the occurrence of this exocytosis is essential for fertilization, recent evidence have provided a molecular context to that demonstration: Izumo1, an essential protein for sperm-egg fusion is relocalized to the proper site only after acrosomal exocytosis occurs. In a broader context, nowadays, the central dogma that prevail for many years, where a capacitated sperm undergo exocytosis after binding to the Zona Pellucida of the egg is under debate since reports from different laboratories have claimed that fertilizing sperm undergo exocytosis prior to interacting with the egg?s extracellular matrix. Today, it is uncertain where and when mammalian sperm trigger exocytosis. And as a consequence of ?where and when?, what is the physiological stimulant(s) of this process? Is there a physiological molecule? Or exocytosis occurs as a result of the continuous destabilization of the acrosomal region during capacitation?. It is our hope that this special volume will serve as a reference for many students and researchers who are interested in this particular type of exocytosis. In this special volume, several leaders of our field have extensively reviewed several topics related to the process of acrosomal exocytosis, covering cellular aspects such as where and when exocytosis occur in mammalian sperm to molecular aspects such as the proteins of the fusion machinery that participate in the last steps of the process.