S100A4

S100A4 Full Name

S100 calcium binding protein A4

S100A4 Introduction

S100 calcium-binding protein A4 (S100A4), historically known as metastasin (MTS1) or fibroblast-specific protein 1 (FSP1), is a prominent member of the S100 family of highly conserved, low-molecular-weight proteins. Characterized by two distinct EF-hand calcium-binding motifs, S100A4 primarily operates as a homodimer. Upon binding to intracellular calcium ions, the protein undergoes a critical conformational shift. This structural rearrangement exposes a hydrophobic cleft, enabling S100A4 to interact with a diverse array of target proteins and thereby serving as a crucial calcium sensor and signal transducer.

Figure 1. The calcium-dependentinteraction of S100A4 with protein targets. (Source: Garrett SC, et al. 2006)

Functionally, S100A4 is highly versatile, exerting its biological influence through both intracellular and extracellular mechanisms. Within the intracellular environment, it predominantly associates with cytoskeletal components, including non-muscle myosin IIA, F-actin, and tropomyosin. By remodeling the actin cytoskeleton and regulating cellular contractility, S100A4 significantly enhances cell motility, invasion, and directional migration. In addition to its intracellular roles, S100A4 is actively secreted into the surrounding microenvironment by various cells, including macrophages and fibroblasts. Extracellular S100A4 acts in an autocrine or paracrine fashion, primarily binding to cell surface receptors such as the receptor for advanced glycation end products (RAGE) and Toll-like receptor 4 (TLR4). This interaction activates downstream signaling cascades—such as the NF-κB and MAPK pathways—which collectively stimulate cell proliferation, survival, angiogenesis, and inflammatory responses.

In the clinical landscape, the dysregulation of S100A4 is intimately linked to the pathogenesis of several severe diseases, most notably aggressive malignancies. Its overexpression is universally recognized as a major driver of cancer metastasis and is considered a robust prognostic biomarker for poor clinical outcomes in breast, colorectal, lung, prostate, and pancreatic cancers. S100A4 heavily promotes the epithelial-mesenchymal transition (EMT), facilitating the escape of tumor cells from the primary site. Beyond oncology, S100A4 is a hallmark protein in the progression of fibrotic diseases. It is widely used as a marker for active, matrix-producing fibroblasts in pulmonary, renal, and hepatic fibrosis. Furthermore, its potent pro-inflammatory properties heavily implicate S100A4 in autoimmune and chronic inflammatory conditions, such as rheumatoid arthritis, positioning the protein as a highly promising therapeutic target across multiple disease spectrums.

Alternate Names for S100A4

S100A4; S100 calcium binding protein A4; 42A; 18A2; CAPL; FSP1; MTS1; P9KA; PEL98; protein S100-A4; protein Mts1; fibroblast-specific protein-1; placental calcium-binding protein; malignant transformation suppression 1; leukemia multidrug resistance associated protein; S100 calcium-binding protein A4 (calcium protein; calvasculin; metastasin; murine placental homolog); LK-1

• 1. Garrett SC, et al. S100A4, a mediator of metastasis. J Biol Chem. 2006 Jan 13;281(2):677-80.
  2. Fei F, et al. S100A4 in cancer progression and metastasis: A systematic review. Oncotarget. 2017 May 19;8(42):73219-73239.