Recombinant Mouse PDZK1-interacting protein 1 (Pdzk1ip1)

Protein Identification and Nomenclature

PDZK1-Interacting Protein 1 (PDZK1IP1) is a small protein that has been identified under multiple names in scientific literature, including MAP17, DD96, and SPAP . Initially characterized as an epithelium-specific molecule, this protein has subsequently garnered attention due to its significant expression in various carcinomas and its role in multiple signaling pathways . The human gene is cataloged under NCBI gene ID 10158 and is recognized in the HGNC database under ID 16887 .

Expression and Purification Systems

Recombinant mouse Pdzk1ip1 protein represents an important tool for investigating the protein's functions in controlled experimental settings. While the search results do not provide specific details about production methods for mouse Pdzk1ip1, recombinant proteins are typically produced using expression systems such as bacterial (E. coli), yeast, insect, or mammalian cell cultures that have been engineered to express the target protein.

Comparative Analysis of Human and Mouse PDZK1IP1

Mouse and human PDZK1IP1 share significant homology, though species-specific differences exist that may influence experimental outcomes when using recombinant mouse protein in research. The functional domains identified in human PDZK1IP1, particularly the critical N-terminal region between positions 40-49 that mediates Smad4 interaction, likely have analogous regions in the mouse protein due to evolutionary conservation of signaling pathway components .

Regulation of TGF-β Signaling Pathway

PDZK1IP1 exhibits significant activity in the regulation of the Transforming Growth Factor-β (TGF-β) signaling pathway. Experimental evidence indicates that PDZK1IP1 directly interacts with Smad4, a critical mediator in the TGF-β signaling cascade . This interaction results in the inhibition of both TGF-β and bone morphogenetic protein (BMP) signaling pathways . Rather than affecting the phosphorylation of receptor-regulated Smads (R-Smads), PDZK1IP1 appears to interfere with the formation of the R-Smad/Smad4 complex that typically occurs following TGF-β stimulation .

Notably, PDZK1IP1 has been shown to retain Smad4 in the cytoplasm of TGF-β-stimulated cells, preventing its nuclear translocation and subsequent activation of target genes . Knockdown experiments have demonstrated that reduction of PDZK1IP1 enhances the expression of TGF-β target genes such as Smad7 and TMEPAI upon TGF-β stimulation, while overexpression of PDZK1IP1 suppresses TGF-β-induced reporter activities .

Interaction with Smad Proteins

The interaction between PDZK1IP1 and Smad proteins represents a key mechanism by which PDZK1IP1 exerts its regulatory functions. Experimental findings demonstrate that PDZK1IP1 interacts with multiple Smad proteins, including Smad2, Smad3, and Smad4, with the interaction dependent on ALK5 activation . Particularly strong interactions have been observed between PDZK1IP1 and both Smad2 and Smad4 . Additionally, interaction with Smad8 and Smad4 can be detected upon BMP receptor activation .

Proximity ligation assays have confirmed the endogenous interaction between PDZK1IP1 and Smad4, with the interaction becoming visible following TGF-β stimulation . Molecular analysis has further determined that PDZK1IP1 specifically interacts with the MH1 domain of Smad4, potentially creating steric hindrance that prevents the association between receptor-regulated Smads and Smad4 .

Expression in Carcinomas

PDZK1IP1 has been found to be expressed at elevated levels in various human carcinomas, suggesting its potential role in tumor development and progression . Specifically, overexpression of PDZK1IP1 has been identified in intrahepatic cholangiocarcinoma (iCCA), as demonstrated through RNA-Seq data analysis comparing tumor and para-tumor tissue samples . This finding suggests that PDZK1IP1 might serve as a biomarker for certain types of cancer .

Effects on Cell Proliferation, Migration, and Invasion

PDZK1IP1 appears to influence multiple cellular processes that are relevant to cancer progression. Research has shown that overexpression of PDZK1IP1 inhibits TGF-β-induced cell migration and significantly suppresses TGF-β-mediated cell growth arrest in A549 cells . Furthermore, PDZK1IP1 has been reported to inhibit tumor necrosis factor-α-induced G1 arrest by impairing p21 induction .

In a xenograft tumor model where TGF-β was previously shown to have tumor-promoting effects, gain of function of PDZK1IP1 resulted in decreased tumor size and increased survival rates . Paradoxically, PDZK1IP1 has also been associated with tumorigenicity in other contexts, with PDZK1IP1-expressing cells shown to proliferate in nude mice . This suggests that the protein's effects may be context-dependent and influenced by other factors in the cellular environment.

Regulation of Reactive Oxygen Species

PDZK1IP1 has been associated with increased levels of reactive oxygen species (ROS), which correlate with its effects on tumorigenicity . Treatment of PDZK1IP1-expressing cells with antioxidants has been reported to lead to a loss of tumorigenicity, suggesting that ROS generation may be one mechanism through which PDZK1IP1 exerts its effects .

Modulation of Notch Signaling

Beyond its effects on TGF-β signaling, PDZK1IP1 has been shown to activate Notch signaling to regulate cancer stem cell pools . This suggests that PDZK1IP1 may influence cellular differentiation and stemness properties, which can contribute to tumor initiation and progression.

Maintenance of PI3K/Akt Signaling

PDZK1IP1 has been found to decrease c-Myc-mediated caspase3-like activity in Rat1 fibroblasts under low serum conditions, thereby maintaining the phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway . This action may contribute to the pro-survival and proliferative effects observed in PDZK1IP1-expressing cells.

In Vitro Functional Studies

Recombinant mouse Pdzk1ip1 provides a valuable tool for investigating the protein's functions in controlled experimental settings. Applications include studies of protein-protein interactions, particularly with components of the TGF-β signaling pathway; analysis of effects on cell migration, proliferation, and invasion; and examination of the protein's impact on gene expression profiles.

Therapeutic Target Exploration

Given PDZK1IP1's role in multiple cancer types and its involvement in key signaling pathways, recombinant Pdzk1ip1 can facilitate research into potential therapeutic approaches. Studies using recombinant protein can help identify small molecules or biologics that may modulate PDZK1IP1 function, potentially leading to novel cancer treatments.

References

1. PDZK1-interacting protein 1 (PDZK1IP1) traps Smad4 protein and suppresses transforming growth factor-β (TGF-β) signaling

2. PDZK1IP1 (PDZK1 interacting protein 1)

3. Overexpression of PDZK1IP1, EEF1A2 and RPL41 genes in intrahepatic cholangiocarcinoma

4. PDZK1IP1 gene promotes proliferation, migration, and invasion in papillary thyroid carcinoma