C1QBP

Official Full Name

complement C1q binding protein

Organism

Homo sapiens

GeneID

708

Background

The human complement subcomponent C1q associates with C1r and C1s in order to yield the first component of the serum complement system. The protein encoded by this gene is known to bind to the globular heads of C1q molecules and inhibit C1 activation. This protein has also been identified as the p32 subunit of pre-mRNA splicing factor SF2, as well as a hyaluronic acid-binding protein. [provided by RefSeq, Jul 2008]

Synonyms

p32; HABP1; gC1qR; GC1QBP; SF2p32; gC1Q-R; COXPD33; SF2AP32;

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Detailed Information

Recent Research Progress

Complement component 1q subcomponent binding protein (C1QBP), also known as HABP1, p32 and gC1qR, is a ubiquitously expressed, multi-ligand-binding, multi-compartmental cellular protein involved in various ligand-mediated cellular responses. It is widely distributed in the mitochondria, nucleus, cytoplasm, Golgi apparatus and cell membrane, and can be secreted into the extracellular matrix. According to reports, C1QBP is involved in tumorigenesis and cancer progression in various malignancies.

C1QBP and RCC

Renal cell carcinoma (RCC) is the most common kidney tumor arising from the cells in the lining of the kidney tubules. Early studies have shown that androgen receptor (AR) may play a key role in promoting the progression of RCC; however, the detailed mechanism remains unclear. Recent studies have demonstrated higher the nuclease-sensitive element-binding protein 1 (YBX1) expression with lower C1QBP expression in human RCC clinical tissues, and the intensity of C1QBP was inversely correlated with YBX1 nuclear expression. Mechanism anatomy revealed that C1QBP can interact with YBX1 to inhibit YBX1 activation by altering YBX1 phosphorylation and nuclear translocation in RCC cells. The consequences of such suppression of YBX1 may result in inhibition of RCC cell migration and invasion, which involves altering the AR-regulated MMP9 signals. Interruption of this newly identified C1QBP → YBX1 → AR → MMP9-suppressed RCC cell invasion pathway by targeting YBX1 or AR partially reversed the RCC cell invasion. Importantly, results from in vivo mouse model with orthotopic implantation of RCC OSRC2 cells into the left renal capsule also confirmed in vitro cell line studies showing targeting YBX1 could inhibit RCC cell invasion via regulation of AR/MMP9 signals. Collectively, these data indicate that C1QBP can modulate YBX1 to suppress AR-enhanced RCC cell invasion. This newly discovered C1QBP / YBX1 / AR / MMP9 signaling pathway may provide a new potential therapy to better inhibit RCC metastasis.

C1QBP and HSV-1

As a large double-stranded DNA virus, herpes simplex virus type 1 (HSV-1) assembles a capsid in the nucleus where virus particles exit by budding through the inner membrane. Although many viruses and host proteins are involved, the mechanism of viral export not well understood. Recently, when looking for host interacting proteins of ICP34.5, which is a virulence factor of HSV-1, the scholars identified the cellular protein C1QBP by spectrophotometer analysis. When expressed, ICP34.5 is associated with C1QBP in mammalian cells. After HSV-1 infection, C1QBP is recruited to the inner nuclear membrane by ICP34.5, which is parallel to phosphorylation and rearrangement of the nuclear layer. Knockdown of C1QBP in HSV-1 infected cells significantly reduced the production of cell-free virus, indicating that C1QBP is the mediator of HSV-1 nuclear export. These observations indicate that the interaction between HSV-1 ICP34.5 and C1QBP results in disintegration of the nuclear layer and promotes nuclear export of HSV-1 particles.

C1QBP and Pancreatic cancer

Pancreatic cancer shows a significant preference for hepatic metastasis. C1QBP can mediate growth factor-induced cancer cell chemotaxis and distant metastasis by activating receptor tyrosine kinases. Coincidentally, insulin-like growth factor-1 (IGF-1) derived from the liver and cancer cells itself has been identified as a key inducer of hepatic metastasis. Recent studies have confirmed a significant correlation between C1QBP expression and hepatic metastasis in patients with pancreatic cancer. IGF-1 induces the transfer of C1QBP from the cytoplasm to lipid rafts and further promotes the formation of the CD44 variant 6 (CD44v6)/C1QBP complex in pancreatic cancer cells. C1QBP interacts with CD44v6 in lipid rafts to promote phosphorylation of insulin-like growth factor-1 receptor (IGF-1R), thereby activating downstream phosphoinositide 3-kinase (PI3K) and mitogen-activated protein kinase (MAPK) signaling pathways, which mediate the metastatic potential of pancreatic cancer cells, including proliferation, apoptosis, invasion, adhesion and energy metabolism. In addition, C1QBP knockdown inhibited liver metastasis of pancreatic cancer cells in nude mice. Therefore, C1QBP in lipid rafts is considered to be a key regulator of IGF-1 / IGF-1R-induced liver metastasis in pancreatic cancer.

C1QBP and GC

Gastric cancer (GC) remains the fourth largest cancer and the second most deadly cancer in all cancers worldwide. Gao et al. have demonstrated that the expression of C1QBP protein in GC tissues was strongly higher than that in adjacent non-tumor tissues. Increased expression of C1QBP is highly correlated with tumor, node, and metastasis (TNM) stage, depth of invasion, lymph node metastasis, liver metastasis, peritoneal metastasis and poor prognosis, suggesting that C1QBP protein may be an important biomarker for tumor progression and prognosis in patients with GC.

C1QBP and Brain cancer

Recently, some studies have shown that C1QBP in the stimulation of glutamine metabolism by Myc in brain tumors. C1QBP has been shown to be a direct transcriptional target of Myc and its expression contributes to Myc-induced glutamine addiction in cancer cells. C1QBP levels increase in various brain cancers and they are closely related to malignancy grade and Myc expression levels. Attenuation of C1QBP expression in glioma cell lines and patient-derived human glioma cells impairs cell growth in vitro and tumor development in vivo. Taken together, these data provide more mechanistic insight into the reprogramming of glutamine metabolism and how is sustained in the pathogenesis of brain tumors.

C1QBP and BC

Breast cancer (BC) accounts for an estimated 1.38 million of total new cancer cases worldwide, making this disease the most common cancer in the female population. It has been reported that higher C1QBP mRNA levels were observed in tissues from BC patients with lower survival rate and lymph node metastasis. Furthermore, the expression of C1QBP is associated with higher proliferation and motility in BC in vitro. Recently, the C1QBP protein has been shown to be involved in distant metastasis of BC. The same investigator showed that the protein kinase C ξ is an interaction partner of C1QBP that activates the chemotaxis of BC cells.

In conclusion, the abnormal expression of C1QBP is closely related to the progression of various tumors, including RCC, Pancreatic cancer, GC and BC. Therefore, further research on C1QBP is undoubtedly very necessary and valuable.

References:

Dan Yue, et al. C1QBP Regulates YBX1 to Suppress the Androgen Receptor (AR) - Enhanced RCC Cell Invasion. Neoplasia, 2017, 19: 135–144.
Yong Wang, et al. C1QBP suppresses cell adhesion and metastasis of renal carcinoma cells. Scientific Report, 2017: 999.
Wang Y, et al. p32 Is a Novel Target for Viral Protein ICP34.5 of Herpes Simplex Virus Type 1 and Facilitates Viral Nuclear Egress*. Journal Of Biological Chemistry, 2014, 289(52): 35795-35805.
Scully OJ, et al. Complement component 1, q subcomponent binding protein is a marker for proliferation in breast cancer. Experimental Biology And Medicine, 2015, 240(7): 846-853.
Shi HJ, et al. Complement component 1, q subcomponent binding protein (C1QBP) in lipid rafts mediates hepatic metastasis of pancreatic cancer by regulating IGF-1/IGF-1R signaling. International Journal of Cancer, 2017, 141(7): 1389-1401.
Gao HY, et al. Elevated HABP1 protein expression correlates with progression and poor survival in patients with gastric cancer. Oncotargets and Therapy, 2016, 9: 6711–6718.
Fogal V, et al. Mitochondrial p32 is up-regulated in Myc expressing brain cancers and mediates glutamine addiction. Oncotarget, 2015, 6(2): 1157-1170.

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