In order to respond to various external or internal environmental stimuli, organisms develop complex cell signaling pathways consisting of receptors, kinase cascades, and other regulatory proteins. Recently, JMCB has published a number of research articles uncovering new members (Perez et al., 2012; Rayego-Mateos et al., 2013) or regulating mechanisms (Suo et al., 2012; Won et al., 2012; Zhang et al., 2013) of various cell signaling pathways. In this issue, more research works provide new information for understanding the molecular mechanisms and functions of TGF-β signaling as well as other cell signaling pathways for pathological responses.