A growth-dependent post-translational modification of annexin VI.
Annexin VI (p68, 67-kDa calelectrin) is a member of a family of Ca2+/phospholipid-binding proteins, that includes p35 (annexin I) and p36 (annexin II), the major cellular substrates for phosphorylation by the epidermal growth factor receptor and pp60v-src tyrosine kinase activities, respectively. We report here that like annexins I and II, annexin VI is phosphorylated in vivo, but that in contrast, annexin VI phosphorylation is associated with cell growth. In both Swiss 3T3 fibroblasts and human T-lymphoblasts the pattern of phosphorylation followed an almost identical profile. In particular, annexin VI was not phosphorylated in quiescent cells, but was phosphorylated on serine and to a lesser extent threonine, several hours following cell stimulation. Furthermore, annexin VI also incorporated phosphate in a growth-dependent manner, in a form other than a phosphoamino-acid. The phosphate was visualised following acid hydrolysis of immunoprecipitated annexin VI, as part of a complex having high mobility on 2-D thin-layer electrophoresis. The identity of this complex is not known. The results suggest that a post-translational modification other than direct protein phosphorylation may influence the activity of annexin VI and provide evidence linking cell growth with regulation of annexin VI function.
Moss
S E
SE
Department of Physiology, University College London, UK.
Jacob
S M
SM
Davies
A A
AA
Crumpton
M J
MJ
D016475:3T3 Cells; D000818:Animals; D017317:Annexin A6 / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D006133:Growth Substances / Q000494:pharmacology; D006801:Humans; D008214:Lymphocytes; D051379:Mice; D008940:Mitotic Index; D010766:Phosphorylation; D010768:Phosphoserine / Q000032:analysis; D010769:Phosphothreonine / Q000032:analysis; D014176:Protein Biosynthesis
D017317:Annexin A6; D006133:Growth Substances; D010769:Phosphothreonine; D010768:Phosphoserine