Specific changes in protein phosphorylation after chronic desmethylimipramine (DMI) treatment

PharmacologicalReseatchCommunications, Vol. 20, Supplementll, 1988

296 SPECIFIC CHANGES IN

PROTEIN PHOSPHORYLATION AFTER CHROMIC DESMETHYLIXlPRAMINE (DMI)

TREATMENT J. Perez, D. T i n e l l i , S. Ciancio, N. Zanotti, I. Zucchi and G. Racagni* Center of Neuropharmacology, University of Milan and * I n s t i t u t e of Pharmacology, University of Pavia, I t a l y Key words: protein phosphorylation - protein kinase - mlcrotubule - antidepressant drugs ConsJderab|e biological

evidence

indicate

that

several

neurotransmitters

produce many of

their

responses by regu]atJng the i n t r a c e l l u ] a r concentration of cAMP. The diverse

effects of cAMP on cell functions are mediated through the activation of the cAMP dependent protein kinase (cAMP-PK). Pharmacological studies have demonstrated changes in the catalytic a c t i v i t y or in the total amount of the regulatory (R) or catalytic subunit (C) of the enzyme (Lohman and Walter, IgB4). These experiments suggest that cAMP-PK plays an important role in regulating c e l l u l a r processes. I t has been demonstrated that chronic administration of DMI is

assoclated with

adaptive

changes in

the 8-adrenergJc

receptors linked to adenylate

cyclase a c t i v i t y (Brunel~o et at. 1985). Our studies demonstrate an increase in the protein band of apparent m.w. 56 Kd in the soluble fraction of rat cerebral cortex after chronic DMl treatment.

Elution

profile,

molecular

weight and autophosphorylation suggest that this

protein might be the R subunit of cAMP-PK type IT, Some evidence indicate that cAMP-PK is associated

with i n t r a c e l l u l a r structures including microtubules (Lohman and Walter, 1984). 3 Therefore, we have studied H-cyclic AMP binding, photoaffinlty labeling and phosphorylatlon status

of

the

crude microtubule

fraction

of

rat

cerebral

cortex

after

chronic DMI

administration. In these conditions, in line with the previous reported increase of RII, we have detected a higher incorporation of

32p in the MAP and an increase in the specific 3 2 32 H-cAMP binding and photoactivated incorporation of B-N-3- P-cAMP. REFERENCES: Lohmann, S.Z. and Walter O. (ig84) in Advances Cyclic Mucleotide and Protein Phosphorylation Research, Greengard et al. Eds. Raven Press New York, 63-i17 Brunello N., Mocchetti I . , Volterra A., Cuomo V. and Racagni G. (Ig85) Psychopharmacol. But1. 21, 3?9-384