R-spondins: Multi-mode WNT signaling regulators in adult stem cells

R-spondins (RSPOs) are secreted cysteine-rich glycoproteins that belong to a superfamily of thrombospondin type 1 repeat-containing proteins. RSPOs together with WNT proteins potentiate canonical WNT/β-catenin signaling activity. Over the last several years, the understanding of the regulatory mechanisms and functional roles of RSPOs in many biological contexts has increased. Particularly, because a leucine-rich repeat containing G...