C1QC

Background

Complement C1, the first member of the classical complement pathway, is a protein complex composed of the subcomponents C1q, C1r, and C1s. Among these subcomponents, C1q is a 460 kDa protein made up of 18 polypeptide chains, 6 C1QA, 6 C1QB, and 6 C1QC chains, respectively. Human complement C1q subcomponent subunit C (C1QC) is a 24 kDa polypeptide chain with 245 amino acids forming a lollipop-like structure. In the lollipop-like structure of C1QC, about 81 amino acids near the N terminus yield the collagen-like ‘rod’, and ~136 residues at the C terminal form the globular ‘head’ structure. The collagen-like region of C1QA, C1QB, and C1QC link to each other forming a triple-helical structural strand. And then C1QC of one strand is linked to the adjacent C chain by a disulfide bond forming an ABC-CBA doublet. 6 such triple helical strands or 3 ABC-CBA doublets non-covalently combine resulting in the intact complement C1q with a bouquet-like structure.

The human C1QA, C1QB, and C1QC encoded genes are arranged in the order A-C-B on chromosome 1. Abnormal expression of any C1QA, C1QB, and C1QC will lead to defective C1q function, causing the C1q to fail to bind to antigen-antibody complex and activate the classical complement pathway. Deficiency of C1QC or C1q has been associated with immunodeficiency and autoimmune diseases.

Fig.1 Structure and assembly of C1QC subunit.^{1, 3}

C1QC Functional Service

Creative Biolabs offers a broad spectrum of C1QC-focused products, such as anti-C1QC antibodies, ELISA kits, recombinant C1QC proteins, and reporter vectors featuring C1QC clones. These carefully crafted reagents are crucial for unraveling the interactions of C1QC proteins with various molecular entities, thereby supporting research endeavors dedicated to the development of therapeutic strategies for a range of diseases.

Fig.2 Expression analysis of C1QC.^{2, 3}

Kidney renal clear cell carcinoma (KIRC), a subtype of renal cell carcinoma, is characterized by distinct immunogenicity and impaired immune infiltration. C1QC plays a role in tumor development and tumor microenvironment regulation. By employing TIMER and TCGA portal databases, researchers discovered significant differences in C1QC expression between tumor and normal tissues, further validated by the Human Protein Atlas. C1QC levels, found to be elevated in KIRC tissues, correlated positively with tumor stage, grade, and nodal metastasis, and negatively with prognosis. Knockdown experiments indicated reduced proliferation, migration, and invasion of KIRC cells. Moreover, C1QC exhibited a strong association with immune cells, notably macrophages, within the tumor context. The results indicate that C1QC could serve as a potential prognostic indicator and therapeutic target in KIRC.

Creative Biolabs delivers an extensive portfolio of services that focus on C1QC functionality, featuring C1QC-binding assays and a range of specialized functional assessments. These services are carefully crafted to support our esteemed clients in achieving their clinical and research ambitions.

References

1. Ain, Danyaal, et al. "The role of complement in the tumor microenvironment." Faculty Reviews 10 (2021).
2. Hu, Yu-Lan, et al. "Characterization of C1q in teleosts: insight into the molecular and functional evolution of C1q family and classical pathway." Journal of Biological Chemistry 285.37 (2010): 28777-28786.
3. Distributed under Open Access license CC BY 4.0, without modification.