Glycosyl phosphatidylinositol (GPI)/inositolphosphate glycan (IPG): An intracellular signalling system involved in the control of thyroid cell proliferation

In porcine thyrocytes, TSH alone does not induce cell growth. Recently, it has been demonstrated that acute stimulation by TSH of porcine thyrocytes l eads to release an inositolphosphate glycan (IPG) described as a putative s econd messenger for various growth factors in different cell types. IPG iso lated from porcine thyrocytes induces proliferation of fibroblasts EGFR T17 and porcine thyrocytes. In porcine thyrocytes we have confirmed that cell growth requires the presence of both TSH and insulin. This effect is reprod uced by 8-bromo cyclic AMP suggesting a mediation by intracellular cyclic A MP. Cooperative effects between 8-bromo cyclic AMP and IPG have also been e videnced and are in favour of a crosstalk between distinct signalling pathw ays. (C) Societe francaise de biochimie et biologie moleculaire / Elsevier, Paris.