P21- ACTIVATED KINASE 4 AND ACTIN CYTOSKELETON DYNAMICS

Abstract

P21-ACTIVATED KINASE 4 (PAK4), A SERINE/THREONINE KINASE FROM THE GROUP II PAK FAMILY KINASES, IS ONE OF MANY ACTIN DYNAMICS REGULATORS THAT CONTROL THE FORMATION OF ACTIN-RICH STRUCTURES SUCH AS FILOPODIA IN MAMMALIAN CELLS. PAK4 PHOSPHORYLATES LIM KINASE (LIMK), WHICH IN TURN, PHOSPHORYLATES THE ACTIN DEPOLYMERISATION FACTOR, COFILIN. COFILIN PHOSPHORYLATION RESULTS IN THE STABILISATION OF THE FILAMENTOUS FORM OF ACTIN. THE PRIMARY GOALS OF THIS PROJECT WERE TO 1) UNDERSTAND HOW THE KINASE DOMAIN OF PAK4 IS INHIBITED BY INCA (INDUCED IN NEURAL CREST BY AP2); AND 2) TO EXPLORE THE DIVERSITY OF ACTIN BINDING PROTEINS (ABPS) IN THE ACTIN POLYMERISATION AND DEPOLYMERISATION CASCADES DOWNSTREAM SIGNALLING CASCADES, SUCH AS PAK4.

THE FIRST OBJECTIVE WAS ACHIEVED BY CRYSTALLISING THE PAK4: INCA COMPLEX IN VIVO. THIS NOVEL STRUCTURE OF THE PAK4 KINASE DOMAIN IN COMPLEX WITH INCA AND ATP WAS SOLVED AT A RESOLUTION OF 2.95 ?. THE STRUCTURE REVEALED THAT PAK4 BINDS TO ITS INTRAMOLECULAR AUT