Question: Describe the known functions for the prothymosin alpha c-terminal peptide?

Context:
The C-terminal decapeptide of prothymosin α is responsible for its stimulatory effect on the functions of human neutrophils in vitro
In this study, we investigated the ability of the immunoreactive fragment of the polypeptide prothymosin alpha (proTα), i.e., the decapeptide proTα(100-109), to enhance the functions of neutrophils isolated from the peripheral blood of breast cancer patients in comparison with those from healthy donors.
Our results suggest that proTα(100-109) activates neutrophils, particularly those derived from breast cancer patients
The Ca²(+)-dependent interaction between ProTα and S100A13 was found to require the C-terminal peptide sequences of both proteins.
When cells were administered apoptogenic compounds, ProTα was cleaved by caspase-3 to generate a C-terminal peptide-deficient fragment, which lacks the nuclear localization signal (NLS).
Prothymosin alpha immunoactive carboxyl-terminal peptide TKKQKTDEDD stimulates lymphocyte reactions, induces dendritic cell maturation
Prothymosin alpha (ProTalpha) is a small acidic polypeptide with important immunostimulatory properties, which we have previously shown to be exerted by its carboxyl (C)-terminus
Here, we assayed the activity of synthetic peptides homologous to ProTalpha's C-terminus to stimulate lymphocyte functions, in particular natural killer cell cytotoxicity of peripheral blood mononuclear cells isolated from healthy donors. A synthetic decapeptide TKKQKTDEDD was identified as the most potent lymphocyte stimulator. The activity of this peptide was sequence-specific and comparable to that of the intact molecule, suggesting that ProTalpha's immunoactive segment encompasses the nuclear localization signal sequence of the polypeptide.
These data, in conjunction with reports showing that the peptide TKKQKTDEDD is generated in vivo upon caspase-cleavage of ProTalpha during apoptosis, strengthen our hypothesis that immune response stimulation by ProTalpha is in principle exerted via its bioactive C-terminal decapaptide, which can acquire a sequence-specific beta-sheet conformation and induce DC maturation.
Ability to stimulate p53-dependent transcription was lost by C-terminal mutants of prothymosin alpha with impaired nuclear accumulation, but not by N-terminal deletion mutants and by the double mutant of prothymosin alpha with impaired ability to bind Keap1, suggesting that prothymosinalpha-Keap1 interaction is dispensable for p53 response.
We found that zinc binding causes partial folding of the C-terminal half of ProTalpha, especially the Glu-rich region
The immunologically active site of prothymosin alpha is located at the carboxy-terminus of the polypeptide.
. ProTalpha(89-102) and proTalpha(103-109) significantly fortified healthy donor-lymphocytes' immune responses to levels comparable to those induced by intact proTalpha. These effects were more pronounced in cancer patients, where peptides proTalpha(89-102) and proTalpha(103-109) partly, however significantly, restored the depressed AMLR and cytolytic ability of PBMC, by simulating the biological activity exerted by intact proTalpha.
This is the first report showing that proTalpha's immunomodulating activity can be substituted by its C-terminal peptide(s)
The peptide (1-88) of calf prothymosin alpha is shown not to accumulate in the Xenopus nucleus, demonstrating that the C-terminal 21 residues, which include a KKQK sequence, are required for nuclear migration.
fProt-alpha contains 28 aspartic and 25 glutamic acid residues and presents the typical basic KKQK amino acid sequence in the close carboxyl terminal region
This is the first report showing that proTalpha's immunomodulating activity can be substituted by its C-terminal peptide(s).

Answer: Prothymosin alpha (ProTα) (encoded in human by the PTMA gene) is a ubiquitous, highly acidic nuclear polypeptide. During early apoptosis, proTα is cleaved by activated caspase-3, with a primary attach site being D99, close to its carboxyl-terminus. The role of the cleaved decapeptide -- proTα(100-109) -- is not fully understood. proTα(100-109), which contains the nuclear localization signal (NLS) for ProTα, has been demonstrated to have immunostimulatory properties, such as to stimulate lymphocytes and neutrophils and induce dendritic cell maturation.