AKAP82 and compartmentalization of signaling in sperm

University Of Pennsylvania, Philadelphia PA

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Abstract

DESCRIPTION (provided by applicant): The mammalian spermatozoon is a highly compartmentalized, polarized cell which has but one function, i.e., to fertilize an egg. This cell contains several organelles and compartments, many of them unique, with each one functioning in an independent, yet coordinated manner. During spermiogenesis, the structure of the cell is remodeled, resulting in the compartmentalization of the cell's various functions (e.g., egg recognition on the surface of the head, motility generated by the entire flagellum). The cAMP-dependent protein kinase A (PK-A) regulates a broad variety of cellular activities in both somatic, and germ cells and sperm. While PK-A is regulated temporally by the second messenger cAMP, spatial regulation within cells occurs by compartmentalization via A-Kinase Anchor Proteins (AKAPs). These proteins tether PK-A through the regulatory subunits of the kinase to various cellular structures, placing the kinases in close proximity with both their upstream effector molecules and downstream targets and facilitating the propagation of second messenger signals. The major structural protein of the mouse fibrous sheath (FS), a cytoskeletal structure in the sperm tail, is AKAP82. The finding that AKAP82 tethers PK-A suggests that it acts as a scaffolding protein for regulatory proteins in the tail. The long-term goal of this research is to understand the role of AKAP82 as an anchoring protein for signaling and metabolic molecules in sperm. The following specific aims are proposed: 1) To examine the role of AKAP82 in the assembly of the FS; 2) To study proteins that interact with AKAP82 in the FS; 3) To examine the post-translational modifications such as phosphorylation of AKAP82; and, 4) To examine the transcriptional regulation of the AKAP82 gene. The presence of scaffolding proteins such as AKAP82 can act to establish and integrate signaling and metabolic pathways. Studies of such scaffolding proteins and their function are important for the understanding of several processes of male reproductive biology.