Serum amyloid A-2 protein (SAA2)

Function
Serum amyloid A (SAA) proteins function as cytokine-like proteins with roles in the acute phase response, lipid transport and metabolism, cell-cell communication, atherosclerosis, and feedback in inflammatory, neoplastic, immunologic, and protective pathways ¹. SAA proteins are normally found at low levels in healthy individuals, but after the onset of the acute phase response, SAA levels can increase by 1000-fold within 24 hours, with levels decreasing back to normal when the event resolves. However, elevated levels of SAA can persist when inflammation is chronic. Acute-phase SAA is tightly bound to high-density lipoprotein (HDL) and functions as an apolipoprotein.

Mechanism and pathways
The human genome encodes four major variants of SAA (SAA1-4), with SAA3 being a transcribed pseudogene ¹. SAA1 and SAA2 are involved in the classic acute phase response and are synthesized and secreted by the liver (hepatocytes), macrophages, adipocytes, kidney, lung, and mammary gland cells. Transcription of Saa1 and Saa2 is also observed in synovial and brain cells. During the acute phase response, SAA1 expression is regulated by many transcription factors (NF-κB, C/EBP, YY1, AP-2, SAF, Sp1, STAT3), proinflammatory cytokines (IL-1β, IL-6, TNF-α), and glucocorticoids ². SAA4 is constitutively expressed ¹.

SAA2 is found at high levels in lung adenocarcinoma samples, and, in mice, overexpression of SAA2 results in metastasis ³. SAA2 abundance is also positively correlated with the disease stage of non-small cell lung cancer and has been suggested as a diagnostic biomarker ⁴. Additionally, in mice, increased SAA2 levels are associated with preterm delivery ⁵.

Structure
Mature SAA2 protein consists of 104 amino acids and is a hexamer stabilized by its C-terminal tail ². SAA proteins are poorly soluble in aqueous solutions, and concentrations needed to characterize their 3D structure are difficult to acquire ¹. Heparin sulfate disrupts SAA binding to HDL.

Human

MRSFFSFLGEAFDGARDMWRAYSDMREANYIGSDKYFHARGNYDAAKRGPGGAWAAEVISNARENIQRLTGHGAEDSLADQAANKWGRSGRDPNHFRPAGLPEKY

Lyophilized

~15 kDa

~12 kDa

0.22μm filtered

After reconstitution this protein is stable for 1 month at 2-8°C. For long term storage, store at -20 to -80 °C.

Frozen Dry Ice

Human

Research Use Only

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