PAWR (PRKC apoptosis WT1 regulator protein; Prostate apoptosis response-4, Par-4)

2016-01-01   Nidhi Shukla , Yanming Zhao ,  , Vivek Rangnekar 




Review on PAWR, with data on DNA, on the protein encoded, and where the gene is implicated.



Genomic regions: Par-4/PAWR gene is encoded by the minus strand of chromosome 12q21.2. The gene encompasses 99.064 kb of DNA; 7 exons and 6 introns. ATG is located on exon 2.


2.2 kb nucleotides mRNA. 1.02 kb open reading frame.


Not known.



Human Par-4/PAWR is a about 40 kDa protein containing 340 amino acids. Rat Par-4 has 332 amino acids whereas mouse Par-4 has 333 amino acids. Par-4/PAWR has two putative nuclear localization sequences in the N-terminal region and a leucine zipper domain and a nuclear export sequence in the C-terminal portion. There is a SAC domain (147-206 amino acids), selective for apoptosis induction in cancer cells. SAC domain is the effecter domain of Par-4/PAWR. These domains are 100% conserved in human, rat and mouse homologs.


Par-4/PAWR is ubiquitously expressed in normal mammalian tissues. However, Par-4/PAWR is diminished in a majority (>75% specimens) of renal cell carcinoma specimens. Par-4/PAWR expression is also decreased in endometrial tumors, lung cancer, neuroblastoma and in cells of patients with acute lymphatic leukemia and chronic lymphocytic leukemia. Par-4 is down-regulated in breast cancer, nasopharyngeal tumors and glioblastoma, and this is associated with therapy resistance and reduced patient survival.


Immonocytochemical analysis indicates that Par-4/PAWR is predominantly localized in cytoplasm in normal cells and is strongly localized in cytoplasm and nucleus in most cancer cell lines. However, Western blot analysis indicates that Par-4/PAWR is also in the nuclear fraction of normal cells implying it is masked in the nucleus. Par-4 is spontaneously secreted by normal and cancer cells, and secreted Par-4 induces cancer-cell specific apoptosis through cell surface receptor GRP78, expressed at the surface of only cancer cells, not normal cells.


Par-4/PAWR, a pro-apoptotic protein, was first identified in prostate cancer cells that were induced to undergo apoptosis. Par-4 knockout mice spontaneously develop tumors of the liver, lung, and endometrium; prostatic intraepithelial neoplasia, and an increased frequency of estrogen-inducible tumors in the endometrium and BBN-inducible tumors in the bladder. Endogenous Par-4/PAWR expressed in normal and cancer cells does not, by itself, causes apoptosis, yet is essential for apoptosis via diverse cell death pathways. Par-4/PAWR sensitizes cells to apoptosis by wide variety of pro-apoptotic stimuli, such as growth factor withdrawal, agents that elevate intracellular Ca2+, TNF, TRAIL, UV, X-ray and gamma irradiation, or IFN-gamma. Ectopic Par-4/PAWR over-expression is by itself sufficient to induce apoptosis in most cancer cells, but not in normal or immortalized cells. The cancer selective pro-apoptotic function of Par-4/PAWR is localized in its central core SAC (Selective for Apoptosis-induction in Cancer cells) domain (amino acids 147-206 in human Par-4/PAWR; or 137-195 in rat Par-4) which is 100% conserved in human, mouse and rat. Apoptosis by ectopic Par-4/PAWR requires Par-4/PAWR nuclear translocation and involves both activation of the Fas death receptor signaling pathway and NF-kappaB inhibition. Par-4/PAWR also inhibits the prosurvival protein Bcl-2 and down regulates ERK-2 expression. Neither p53 nor PTEN are directly required for apoptosis by Par-4/PAWR or the SAC domain. Par-4/PAWR has been shown to be i nvolved in suppression of transformation by down-regulation of Ras. Overexpression of Par-4/PAWR results in apoptosis of cells expressing oncogenic Ras.
Several partner proteins of Par-4/PAWR have been identified and partner interaction requires an intact Par-4/PAWR leucine zipper domain. Par-4/PAWR associates with aPKC resulting in inhibition of NF-kappaB activity, interaction with WT1 results in transcriptional repression of Bcl-2, whereas binding to and phosphorylation by Akt1 results in Par-4/PAWR cytoplasm retention by 14-3-3, thus isolating Par-4/PAWR from its nuclear targets. Par-4/PAWR also binds to DLK/ZIP kinase (ZIPK) and induces DAAX/ZIPK-mediated apoptosis. In addition, THAP1 (a novel nuclear pro-apoptotic factor) interacts with Par-4/PAWR and potentiates both serum withdrawal and TNF-induced apoptosis in endothelial cells.
Par-4/PAWR is also involved in sensitization of neurons to apoptosis. Endogenous Par-4/PAWR is reported to be up-regulated in different neurodegenerative diseases including Alzheimers, Huntingtons and Parkinsons diseases and amyotrophic lateral sclerosis.
Post-translational modifications: The apoptosis of Par-4/PAWR requires phosphorylation of the threonine residue (T155 in rat Par-4/PAWR) in the SAC domain by PKA, which is elevated in cancer cells. Amino acid S249 in rat Par-4/PAWR is phosphorylated by AKT for Par-4/PAWR cytoplasm retention and inactivation.
Par-4 is secreted via classical pathway and is associated with ER-stress
Most of the studies until now have been focused on the intracellular role of Par-4 but Burikhanov et al. (2009) provided a new direction to the field with their discovery that Par-4 is secreted by normal or immortalized cells, as well as cancer cells and that secreted Par-4 shows cancer cell-specific apoptosis through cell surface HSPA5 (GRP78), which is an endoplasmic reticulum (ER)-resident protein expressed at the cell surface selectively in cancer cells. Par-4 secretion is observed in vivo and plasma or serum samples obtained from Par-4 transgenic mice contain detectable amounts of Par-4 that are adequate to induce apoptosis ex vivo specifically in cancer cells. Cells treated with Brefeldin A (BFA, an antiviral antibiotic, which blocks protein trafficking from the ER to cis-Golgi cisternae), decreased secretion of Par-4, suggesting that the secretion of Par-4 occurs through a BFA-sensitive classical pathway involving the ER-Golgi network. Also, Par- 4 secretion is increased upon treatment of cells with ER stress inducers tunicamycin (an inhibitor of N-linked glycosylation) and thapsigargin (an inhibitor of the sarcoplasmic/Endoplasmic Reticulum Ca+2 ATPase), which also caused upregulation of GRP78.
Par-4 is involved in the translocation of GRP78 from ER to the cell surface
The correlation between intracellular Par-4, GRP78 and extracellular Par-4 in activating apoptosis has been further confirmed through RNAi studies. Knocking down Par-4 resulted in decreased translocation of GRP78 to the cell surface, indicating that endogenous Par-4 is required for cell surface expression of GRP78. This finding was further supported by Cohen et al. who confirmed the role of endogenous Par-4 in binding and translocation of GRP78 in trophoblastic cells. For the first time, this study showed the presence of Par-4 in both villous and extra villous cytotrophoblastic cells (CTB) and expression of Par-4 correlated with expression of membrane GRP78. Also, Par-4 overexpression led to an increase in cell surface expression of GRP78, whereas reduced Par-4 expression resulted in reduced cell surface localization of GRP78. The observations corroborate the role of Par-4 in translocation of GRP78 from ER to the cell surface. Decreased membrane GRP78 expression has been observed in preeclamptic (PE) cytotrophoblastic cells (CTB). This could be due to an altered expression of GRP78 transporting proteins. Interestingly, Par-4 protein expression was found to be reduced in PE CTB. This finding will help in better understanding of Par-4 expression, localization and posttranslational modifications in CTB to prevent PE.
Par-4/SAC-activity is transferable by bone marrow transplantation
To analyze the functional efficacy of SAC domain, transgenic mice that ubiquitously express the SAC domain were generated. To confirm the functional activity of this secreted Par-4/SAC in transgenic mice, bone marrow of SAC-GFP-transgenic mice, littermate control mice or GFP-transgenic control mice was transferred to irradiated littermate control mice. Serum samples obtained from mice that received bone marrow cells from SAC-GFP-transgenic mice, but not from littermate control or GFP-transgenic mice, induced apoptosis of aggressive Lewis Lung Carcinoma (LLC1) cells in culture. This finding implies that Par-4/SAC is secreted and that bone marrow transplantation is effective in transferring cells capable of secreting transgenic SAC-GFP activity into recipient mice.
Inhibition of lung metastasis in mice by recombinant Par-4/SAC
To further confirm that Par-4/SAC activity in serum of transgenic mice had the potential to inhibit metastasis, recombinant TRX-Par-4 or TRX-SAC protein, which induced apoptosis of cancer cells but not non-transformed cells in culture, was used. TRX-Par-4 or TRX-SAC but not TRX control protein, induced apoptosis in LLC1 and PC-3 cell cultures but not in non-transformed BPH1 cell culture. Also, recombinant Par-4 or SAC protein when introduced intravenously in immunocompetent C57BL/6 mice significantly inhibited lung metastasis of LLC1 cells. These findings confirmed that Par-4/SAC is secreted by normal cells and is systemically active for an extended period of time in suppressing tumor growth and metastasis in mice. A majority of the tumor suppressor proteins have exclusive intracellular mode of action, this induction of both extracellular and intracellular apoptotic pathways by Par-4/SAC is unique and can be harnessed for cancer-selective therapeutics.
Empowering Normal Cells for Paracrine Inhibition of Cancer
I- P53 induces Par-4 secretion by downregulating UACA
TP53 also known as the "guardian of the genome" acts as a tumor suppressor by intracellular activation of growth arrest and apoptotic cell death pathways. Owing to its prominent role as a tumor suppressor and involvement in apoptotic pathways, p53 is mutated in over 50% of cancers. Mutant forms of p53 may render cancer cells resistant to both chemotherapy and radiation therapy. Burikhanov et al. (2014) have shown that activation of p53 function in normal cells causes paracrine growth inhibitory effects in cancer cells by systemically inducing secretion of Par-4. Interestingly, secreted Par-4 mediates a paracrine growth-inhibitory effect by inducing apoptosis of p53-deficient cancer cells. In a search for the direct target of p53 for inducing Par-4 secretion, UACA, which is a binding partner of Par-4, was identified. Previous studies have shown that UACA binds to Par-4 and prevents its secretion. UACA was lower in wild type p53 cells and mouse tissues relative to p53 null cells and mouse tissues, and UACA levels correlated inversely with the levels of Par-4 secreted in the CM. However, knocking down UACA in p53 null MEFs did not increase the secretion of Par-4 indicating that intracellular p53 function is necessary to regulate the secretion of Par-4.
II- Activating p53 induces systemic expression of Par-4 in mice
To investigate the role of p53 in Par-4 secretion in vivo, p53 wild-type mice, p53 null mice, or Par-4 null mice were treated with Nutlin-3a, an activator of p53, and with PS-1145, an inhibitor of NF-kB. Combined treatment of Nutlin-3a and PS-1145 caused a 5-fold increase in serum levels of Par-4 protein in p53 wild-type mice compared to basal levels in serum, whereas it failed to elevate systemic levels of Par-4 in p53 null mice, suggesting that p53 function was essential for upregulation of Par-4 secretion. Interestingly, the serum from Nutlin-3a plus PS-1145-treated p53 wild-type mice, but not p53 null mice or Par-4 null mice, induced ex vivo apoptosis of cancer cell cultures but not normal cell cultures. These findings suggest that p53 activation in normal mice induces adequate levels of systemic Par-4 protein that is functionally effective in inducing apoptosis of cancer cells.
Par-4 secretagogues
As normal cells express wild type p53 function, recent studies have been directed toward utilizing the potential of normal immune cells or non-immune cells to control the growth of tumors. Studies by Burikhanov et al. (2014) suggest a novel cross-talk between p53 and Par-4 where p53 regulates the secretion of Par-4 via classical pathway from normal cells and secreted Par-4 mediates the paracrine apoptotic effects of p53 in a cancer-cell specific manner. Since the levels of Par-4 secreted by normal cells are not adequate to cause massive apoptosis in cancer cell cultures, new compounds and FDA-approved drugs are being actively discovered as Par-4 secretagogues. Burikhanov et al. (2014) have identified a novel secretagogue, Arylquin-1, a 3-arylquinoline, which shows a dose dependent secretion of Par-4 from both normal fibroblasts and epithelial cells. This study identified VIM (vimentin) as a novel binding partner of Par-4 and showed that Arylquin-1 binds to vimentin to release vimentin-bound Par-4 for secretion. Interestingly, Arylquin-1 itself at low nanomolar concentrations (100-500 nM) did not kill normal cells and most cancer cells but it caused robust secretion of Par-4 from normal cells to induce apoptosis of cancer cells only when they were co-cultured.


The Par-4/PAWR gene has been identified in various organisms, including mammals (Pan Troglodytes), rodents (mouse, rat), chicken (Gallus gallus), fish(Zebrafish and Pufferfish) and tadpole. The nuclear localization, leucine zipper, nuclear export and SAC domain sequences are highly conserved.



NOTE Par-4/PAWR mutations are uncommon although a single base mutation (Arg (CGA) 189 (TGA) Stop) localized in exon 3 or the SAC domain has been found in endometrial carcinoma.

Implicated in

Entity name
Breast cancer
Par-4 downregulation promotes breast cancer recurrence
A recent study by Alvarez et al. (2013) has shown that Par-4 is a major underlying factor for breast cancer recurrence. Primary breast tumors consist of a heterogeneous population in which most cancer cells express Par-4 but there are some cells that show lower expression of Par-4. Treatment of tumors with chemotherapeutic agents leads to Par-4 activation that in turn results in multinucleation, p53 stabilization and increased apoptosis, ultimately leading to tumor regression. As a result, in a heterogeneity population of breast tumor, cells with high levels of Par-4 undergo apoptosis after chemotherapy, whereas cells expressing low levels of Par-4 result in recurrence at both local and distant metastatic sites.
Entity name
Malignant gliomas are the most aggressive brain tumor and treating these tumors remains one of the greatest challenges as recurrence is very high even after extensive surgery or chemotherapy. Temozolomide (TMZ) has shown promising activity against gliomas but drug resistance develops in many cases. A novel interaction between PRNP (PrPc), a glycosylphosphatidylinositol-anchored protein and Par-4 has been shown by Zhuang et al. where upon TMZ treatment PrPc interacts with Par-4 via the SAC domain and inhibits Par-4 pro-apoptotic activity. This study shows that the PrPc/Par-4 complex is responsible for protecting the cells against apoptosis by TMZ and that disruption of the PrPc/Par-4 complex induces cell death. This study presents a novel model in which Par-4 acts as ligand for PrPc receptor and interaction between PrPc/Par-4 leads to the anti-apoptotic activity of glioma upon TMZ treatment. A better understanding of PrPc/Par-4 interaction will contribute to the development of strategies for treating glioma cells o the TMZ-based chemotherapy.
Entity name
renal cell carcinoma, and endometrial tumors
Par-4/PAWR is down regulated in over 75% of clear cell type of renal cell carcinoma, and in endometrial tumors. It is mutated within its effector SAC domain in endometrial tumors.


Pubmed IDLast YearTitleAuthors
237700122013Par-4 downregulation promotes breast cancer recurrence by preventing multinucleation following targeted therapy.Alvarez JV et al
196930972009When mutants gain new powers: news from the mutant p53 field.Brosh R et al
252187432014Arylquins target vimentin to trigger Par-4 secretion for tumor cell apoptosis.Burikhanov R et al
115857632001Par-4 drives trafficking and activation of Fas and Fasl to induce prostate cancer cell apoptosis and tumor regression.Chakraborty M et al
242825262013Role of prostate apoptosis response 4 in translocation of GRP78 from the endoplasmic reticulum to the cell surface of trophoblastic cells.Cohen M et al
87978241996The product of par-4, a gene induced during apoptosis, interacts selectively with the atypical isoforms of protein kinase C.Díaz-Meco MT et al
121131202001Temozolomide: a novel oral alkylating agent.Danson SJ et al
177860422007Nutlin-3 inhibits the NFkappaB pathway in a p53-dependent manner: implications in lung cancer therapy.Dey A et al
103918961999Inactivation of the inhibitory kappaB protein kinase/nuclear factor kappaB pathway by Par-4 expression potentiates tumor necrosis factor alpha-induced apoptosis.Diaz-Meco MT et al
109644802000Participation of par-4 in the degeneration of striatal neurons induced by metabolic compromise with 3-nitropropionic acid.Duan W et al
103498401999Prostate apoptosis response-4 production in synaptic compartments following apoptotic and excitotoxic insults: evidence for a pivotal role in mitochondrial dysfunction and neuronal degeneration.Duan W et al
128971272003Identification of a unique core domain of par-4 sufficient for selective apoptosis induction in cancer cells.El-Guendy N et al
31925481988Brefeldin A causes disassembly of the Golgi complex and accumulation of secretory proteins in the endoplasmic reticulum.Fujiwara T et al
162099432005Binding and phosphorylation of par-4 by akt is essential for cancer cell survival.Goswami A et al
97012511998Par-4 is a mediator of neuronal degeneration associated with the pathogenesis of Alzheimer disease.Guo Q et al
156574402005Phosphorylation of Par-4 by protein kinase A is critical for apoptosis.Gurumurthy S et al
106039471998The sarcoplasmic reticulum Ca2+ pump: inhibition by thapsigargin and enhancement by adenovirus-mediated gene transfer.Inesi G et al
97907751998Mapping of the human PAWR (par-4) gene to chromosome 12q21.Johnstone RW et al
186509322008Par-4 inhibits Akt and suppresses Ras-induced lung tumorigenesis.Joshi J et al
129173392003ZIP kinase triggers apoptosis from nuclear PML oncogenic domains.Kawai T et al
129701812003Regulation of mature T lymphocyte proliferation and differentiation by Par-4.Lafuente MJ et al
192507352009EBV LMP-1 negatively regulates expression and pro-apoptotic activity of Par-4 in nasopharyngeal carcinoma cells.Lee JW et al
173323192007Inactivation of the candidate tumor suppressor par-4 in endometrial cancer.Moreno-Bueno G et al
205143952010Down-regulation of the candidate tumor suppressor gene PAR-4 is associated with poor prognosis in breast cancer.Nagai MA et al
105144811999Oncogenic Ras sensitizes cells to apoptosis by Par-4.Nalca A et al
107831452000The prostate apoptosis response-4 protein participates in motor neuron degeneration in amyotrophic lateral sclerosis.Pedersen WA et al
167661272006Doppel-induced apoptosis and counteraction by cellular prion protein in neuroblastoma and astrocytes.Qin K et al
91993161997Expression and function of the leucine zipper protein Par-4 in apoptosis.Sells SF et al
80435201994Commonality of the gene programs induced by effectors of apoptosis in androgen-dependent and -independent prostate cells.Sells SF et al
111626502001Identification of a novel autoantigen UACA in patients with panuveitis.Yamada K et al
216138192011Systemic Par-4 inhibits non-autochthonous tumor growth.Zhao Y et al
213283402012TMZ-induced PrPc/par-4 interaction promotes the survival of human glioma cells.Zhuang D et al

Other Information

Locus ID:

NCBI: 5074
MIM: 601936
HGNC: 8614
Ensembl: ENSG00000177425


dbSNP: 5074
ClinVar: 5074
TCGA: ENSG00000177425


Gene IDTranscript IDUniprot

Expression (GTEx)


Protein levels (Protein atlas)

Not detected


Pubmed IDYearTitleCitations
225325712012Astrocytes secrete exosomes enriched with proapoptotic ceramide and prostate apoptosis response 4 (PAR-4): potential mechanism of apoptosis induction in Alzheimer disease (AD).115
196321852009The tumor suppressor Par-4 activates an extrinsic pathway for apoptosis.89
127174202003THAP1 is a nuclear proapoptotic factor that links prostate-apoptosis-response-4 (Par-4) to PML nuclear bodies.48
97012511998Par-4 is a mediator of neuronal degeneration associated with the pathogenesis of Alzheimer disease.44
128971272003Identification of a unique core domain of par-4 sufficient for selective apoptosis induction in cancer cells.43
173323192007Inactivation of the candidate tumor suppressor par-4 in endometrial cancer.40
156574402005Phosphorylation of Par-4 by protein kinase A is critical for apoptosis.37
126444742003Par-4 transcriptionally regulates Bcl-2 through a WT1-binding site on the bcl-2 promoter.35
186509322008Par-4 inhibits Akt and suppresses Ras-induced lung tumorigenesis.34
237700122013Par-4 downregulation promotes breast cancer recurrence by preventing multinucleation following targeted therapy.34


Nidhi Shukla ; Yanming Zhao ; ; Vivek Rangnekar

PAWR (PRKC apoptosis WT1 regulator protein; Prostate apoptosis response-4, Par-4)

Atlas Genet Cytogenet Oncol Haematol. 2016-01-01

Online version:;-prostate-apoptosis-response-4-par-4)

Historical Card

2007-08-01 PAWR (PRKC apoptosis WT1 regulator protein; Prostate apoptosis response-4, Par-4) by  Yanming Zhao,Vivek Rangnekar 

Markey Cancer Center University of Kentucky Combs Research Building, Room 309 800 Rose Street Lexington, KY 40536, USA