P11, also known as 42C or calpactin I
light chain, belongs to the S100 family of calcium-binding proteins .
The response to elevation of cytoplasmic Ca(2+) levels following extra- or intracellular stimuli is mediated by proteins
that are capable of binding divalent calcium ions. A particular class of these proteins is characterized by the so-called
EF-hand, a helix-loop-helix motif involved in coordinating the Ca(2+) ion. Within the EF-hand superfamily, a distinct
set of proteins is grouped in the so-called S-100 protein family, whose
members share a high degree of sequence similarity with S-100A and S-100B, Ca(2+)-binding proteins originally
isolated from cerebrospinal fluid. Protein p11 (calpactin I, light chain) is a member of the S-100 family but has several
unique features. It has suffered crucial deletions and amino acid substitutions which are thought to render both
Ca(2+)-binding sites inactive. In all tissues and cells studied, p11 is found in a heterotetrameric complex with another
Ca(2+)-binding protein, annexin II (ANX2, LIP2).
Furthermore, overexpression of P11
suppresses apoptosis induced by BAD , suggesting that P11 may be one of the intracellular signal molecules
interacting with the Bcl-2 family of proteins to control apoptosis.
NCBI Summary:
The protein encoded by this gene is a member of the S100 family of proteins containing 2 EF-hand calcium-binding motifs. S100 proteins are localized in the cytoplasm and/or nucleus of a wide range of cells, and involved in the regulation of a number of cellular processes such as cell cycle progression and differentiation. S100 genes include at least 13 members which are located as a cluster on chromosome 1q21. This protein may function in exocytosis and endocytosis.
General function
Intracellular signaling cascade
Comment
Cellular localization
Cytoplasmic
Comment
Ovarian function
Follicle atresia
Comment
Chun et al 2001 reported the expression of messenger ribonucleic acid for the antiapoptosis
gene p11 in the rat ovary and its stimulation by gonadotropins in granulosa
cells of preovulatory follicles.
P11, a member of the S100 family of calcium-binding proteins, has been shown to
interact with BAD (Bcl-xL/Bcl-2-associated death promoter) in the yeast
two-hybrid protein-protein interaction assay. Because overexpression of P11
dampens the proapoptotic activity of BAD in transfected cells, the authors tested the
possibility that the expression of this antiapoptotic protein may be regulated by
gonadotropins and other survival factors in the ovary. Northern blot analysis of
ovaries obtained from prepubertal rats revealed an increased expression of P11
messenger RNA (mRNA) during prepubertal development in the theca cells of
preantral and early antral follicles. Treatment of immature rats with PMSG did not
affect P11 expression, whereas treatment of PMSG-primed rats with an ovulatory
dose of human (h)CG stimulated ovarian P11 mRNA within 6-9 h in the granulosa
cells of preovulatory follicles.
Treatment with other follicle survival factors, including the epidermal growth
factor, the basic fibroblast growth factor, and interleukin-1beta, could also
stimulate P11 expression in cultured preovulatory follicles.