Soluble frizzled-related proteins (sFRPS) function as modulators of Wnt signaling through direct interaction with Wnts. They have a role in regulating cell growth and differentiation in specific cell types. SFRP1 decreases intracellular beta-catenin levels (By similarity). Has antiproliferative effects on vascular cells, in vitro and in vivo, and can induce, in vivo, an angiogenic response. In vascular cell cycle, delays the G1 phase and entry into the S phase (By similarity). In kidney development, inhibits tubule formation and bud growth in metanephroi (By similarity). Inhibits WNT1/WNT4-mediated TCF-dependent transcription. Interacts with WNT1, WNT2, WNT4, WNT8, MYOC and FRZD6. Cell membrane or extracellular matrix-associated. Released by heparin-binding. Highest levels in aortic endothelium, heart, spleen and eye. Lower levels in lung, brain and kidney. Weak expression in liver, skeletal muscle and the medial layer of the aorta. In the cortical brain, localized to neurons and small blood vessels. In the retina, localized to the inner and outer nuclear layers with high expression in the neuronal cell bodies. In the heart, restricted to myocytes. In lung, highest expression found in the epithelium of terminal bronchioles. In kidney, localized to the epithelium of collecting ducts of the medulla and, in spleen, expression restricted to the red pulp in cells associated with the sinuses. The FZ domain is involved in binding with Wnt ligands. Belongs to the secreted frizzled-related protein (sFRP) family.