Descripción del proyecto
DESTABILIZATION AND PROGRESSIVE SYNAPSE LOSS IS A PROCESS THAT OCCURS DURING AGEING AND IN CERTAIN PATHOLOGICAL ALTERATIONS AS ALZHEIMER DISEASE. ALSO, THE DEVELOPMENT OF THE NERVOUS SYSTEM INVOLVES AN INITIALLY EXUBERANT PRODUCTION OF NEURONS THAT ESTABLISH EXCESSIVE SYNAPTIC CONTACTS AND THE SUBSEQUENT REDUCTION IN BOTH NEURONS AND SYNAPSES. THIS DEVELOPMENTAL PROCESS CONSISTS OF AN INITIAL SYNAPSE OVERPRODUCTION TO PROMOTE BROAD CONNECTIVITY AND A SUBSEQUENT ACTIVITY-DEPENDENT REDUCTION IN SYNAPSE NUMBER. THIS ALLOWS CONNECTIVITY TO BE REFINED AND SPECIFICITY GAINED. HEBBIAN COMPETITION BETWEEN THE NERVE TERMINALS OF AXONS WITH DIFFERENT ACTIVITIES SEEMS TO BE THE FUNDAMENTAL CHARACTERISTIC OF THIS PROCESS OF SYNAPSE ELIMINATION, WHICH LEADS TO THE LOSS OF ROUGHLY HALF OF THE OVERPRODUCED ELEMENTS AND THE FUNCTIONAL CONSOLIDATION OF THE REMAINING SYNAPSES IN THE ADULT.IN PREVIOUS STUDIES IN CHOLINERGIC SYNAPSES (MAINLY USING IMMUNOBLOTTING, IMMUNOCYTOCHEMISTRY AND CELLULAR ELECTROPHYSIOLOGY EX VIVO), WE HAVE DESCRIBED A MOLECULAR MECHANISM OF STABILIZATION AND DESTABILIZATION OF THE NEURONAL CONNECTIONS, WHICH ACTS BOTH AT THE PRE- AND POSTSYNAPTIC COMPONENTS DURING DEVELOPMENT AND THAT INVOLVES SEVERAL SIGNALING PATHWAYS. AT THE PRESYNAPTIC LEVEL, WE HAVE DEMONSTRATED THAT THE NEUROTRANSMITTER (ACH) ALSO ACTS ON PRESYNAPTIC CHOLINERGIC MUSCARINIC AUTORECEPTORS (MACHRS: M1, M2 AND M4 SUBTYPES) WHICH MODULATE PROTEIN KINASE ACTIVITY (PKC AND PKA) LINKED TO THE CALCIUM CHANNELS (P/Q, N AND L-TYPES) AND THEN NEUROTRANSMISSION. DIFFERENTIAL ACTIVITY OF THE NERVE TERMINALS RELEASING VARIABLE AMOUNTS OF ACH MAY AFFECT THE MACHRS IN THE NEARBY AXONS AND THUS ALLOWING DIRECT AXONAL COMPETITION. WE DESCRIBED ALSO THE SPECIFIC INVOLVEMENT OF NEUROTROPHINS (BDNF, NT4 AND NT3) AND THEIR RECEPTORS (MAINLY TRKB AND P75NTR). IN THE PRESENT PROJECT, WE WANT TO EXPAND THE KNOWLEDGE OF THIS COMPLEX MOLECULAR MECHANISM WITH THE ANALYSIS OF THE PRESUMED INVOLVEMENT OF THE SYNAPTIC CYTOQUINE MEDIATORS GDNF AND CNTF AND THEIR RECEPTORS (GFR-ALPHA1, CNTFR) AND ADENOSINE AND THEIR RECEPTORS (A1 AND A2A). THE CENTRAL CROSSROAD ROLE OF PKC (EPSILON ISOFORM) IN THE INTRACELLULAR CONVERGENCE OF THESE SIGNALING PATHWAYS WILL BE INVESTIGATED.AT THE POSTSYNAPTIC LEVEL, WE HAVE DEMONSTRATED THAT THROUGH AN ACTIVITY-DEPENDENT PROCESS, A PHOSPHORYLATION OF POSTSYNAPTIC NICOTINIC RECEPTORS (NACHRS) BY PROTEIN KINASE C (PKC) DESTABILIZES THEM, WHILE THE PHOSPHORYLATION OF THESE RECEPTORS BY PROTEIN KINASE A (PKA) STABILIZES THE ACHRS IN THE POSTSYNAPTIC CLUSTER. THE POSTSYNAPTIC DISCONNECTION WOULD DEPEND ON THE EQUILIBRIUM BETWEEN THE PHOSPHORYLATING ACTIONS OF PKC AND PKA. THUS, IT IS IMPORTANT TO UNDERSTAND HOW THE SUBCELLULAR LOCATION OF PROTEIN KINASES C AND A CONTRIBUTES TO THE REGULATION OF PHOSPHORYLATION EVENTS. PROTEIN SCAFFOLD COMPLEXES, LIKE A-KINASE ANCHORING PROTEINS (AKAPS) ARE A KEY MECHANISM BY WHICH A COMMON SIGNALING PATHWAY CAN SERVE MANY DIFFERENT FUNCTIONS. BECAUSE THAT, WE WILL FOCUS IN THE ELUCIDATION OF AKAP FUNCTION IN THE PHOSPHORYLATION OF ACHRS BY PKA AND PKC AT KEY RESIDUES THAT WOULD DEFINE THE STABILITY STATUS OF THE RECEPTORS. ESCONEXION SINAPTICA\KINASAS.\RECEPTORES PURINERGICOS\FACTORES NEUROTROFICOS\NEUROTROFINAS\RECEPTORES MUSCARINICOS\SINAPSIS COLINERGICAS\CANALES DE CALCIO\SINAPSIS NEUROMUSCULAR