sentence: Because putative G protein-independent , “ stand-alone ” β - arrestin signaling downstream of GPCRs lacks valid scientific evidence [ 31 ] and given that whole cell response toward activation of long isoform FFA4 receptors , although largely decreased , was still detectable using a pathway-unbiased holistic biosensor approach reported by Watterson et al. [ 30,32 ] , it is tempting to speculate that it is actually remaining G protein activity downstream of FFAR4 that underlies this bias phenomenon of the short receptor isoform .