Spectrin is an important structural component of the plasma membrane skeleton. The predicted 2,391-amino
acid protein encoded by the SPTBN2 gene, beta-III spectrin, is highly homologous to both beta-I spectrin (SPTB; OMIM 182870)
and beta-II spectrin (SPTBN1; OMIM 182790). Beta-III spectrin contains conserved actin-, protein 4.1-, and ankyrin-binding
domains, membrane association domains 1 and 2, a spectrin dimer self-association site, and a pleckstrin homology domain.
General function
Cytoskeleton
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Cellular localization
Plasma membrane
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Ovarian function
Oogenesis
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β-Spectrin regulates the Hippo signaling pathway and modulates the basal actin network. Wong KK et al. (2015) Emerging evidence suggests functional regulation of Hippo pathway by the actin cytoskeleton, although the detailed molecular mechanism remains incomplete. In a genetic screen we identified a requirement for β-Spectrin in the posterior follicle cells (PFCs) for the oocyte repolarization process during Drosophila mid-oogenesis. β-spectrin mutations lead to loss of Hippo signaling activity in the follicle cells. Similar reduction of Hippo signaling activity was observed after β-Spectrin knockdown in mammalian cells. We further demonstrated that β-spectrin mutations disrupt the basal actin network in the follicle cells. The abnormal stress-fiber-like actin structure on the basal side of the follicle cells provides a likely link between the β-spectrin mutations and the loss of Hippo signaling activity phenotype.//////////////////
Expression regulated by
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Ovarian localization
Oocyte
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Taft RA, et al 2002 reported the identification of genes encoding mouse oocyte secretory and
transmembrane proteins by a signal sequence trap.
At all stages of follicular
development, oocytes interact with surrounding granulosa cells and promote their
differentiation into the types of cells that support further oocyte growth and
developmental competence. These interactions suggest the existence of an
oocyte-granulosa cell regulatory loop that includes both secreted proteins and cell
surface receptors on both cell types. Factors involved in the regulatory loop will
therefore contain a signal sequence, which can be used to identify them through a
signal sequence trap (SST). A screen of an oocyte SST library identified three
classes of oocyte-expressed sequences: known mouse genes, sequences homologous
to known mammalian genes, and novel sequences of unknown function. Many of the
recovered genes may have roles in the oocyte-granulosa cell regulatory loop. For
several of the known mouse genes, new roles in follicular development are implied
by identification of their expression, for the first time, in the oocyte.
Beta spectrin 2 was found by the SST screen.