Role of the kinase activation loop on protein kinase C theta activity and intracellular localisation.
Multiple protein kinase C (PKC) theta species, identified in an erythroleukaemia cell line, have been characterised in terms of their molecular properties and intracellular distribution. PKCthetas localised in the detergent-soluble cell fraction have an Mr of 76 kDa (theta-76) and contain Thr538 or pThr538 in the kinase activation loop. In contrast, PKCthetas localised in the Golgi complex have an Mr of 85 kDa (theta-85) and, although unphosphorylated at Thr538, are catalytically active. Strikingly, only theta-76 species which are unphosphorylated at Thr538 can undergo autocatalytic conversion to theta-85. Moreover, a Thr538-->Ala PKCtheta mutant is constitutively localised in the Golgi complex, confirming that changes in the phosphorylation state of this residue play a pivotal role in the overall control of catalytic properties and localisation of this kinase.
Department of Experimental Medicine, Biochemistry Section, University of Genoa, Viale Benedetto XV, 16132 Genoa, Italy. traspar@unige.it
Bianca
B
Sparatore
Mario
M
Passalacqua
Marco
M
Pedrazzi
Sabina
S
Ledda
Mauro
M
Patrone
Deborah
D
Gaggero
Sandro
S
Pontremoli
Edon
E
Melloni
D000818:Animals; D002384:Catalysis; D002458:Cell Fractionation; D045744:Cell Line, Tumor; D004789:Enzyme Activation; D006056:Golgi Apparatus; D007527:Isoenzymes / Q000378:metabolism*; D051379:Mice; D008856:Microscopy, Fluorescence; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism*; D000074121:Protein Kinase C-theta; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D013912:Threonine / Q000378:metabolism
D007527:Isoenzymes; D013912:Threonine; C489593:Prkcq protein, mouse; D011493:Protein Kinase C; D000074121:Protein Kinase C-theta