...
columns: [{
    header: 'Name',
    dataIndex: 'Name',
    sortable: true,
    doSort: function(state){
        var ds = this.up('tablepanel').store;
        ds.sort({
            property: 'SortOrder',
            direction: state
        });
    }
    ....
}]

columns: [
    {
        header: 'Name',
        dataIndex: 'Name',
        listeners: {
            headerclick: function() {
                var store = this.up('grid').getStore();
                store.sort({
                        property: 'SortOrder',
                        direction: this.sortState
                    });
            }
        }
    }
 ]

columns: [
    {
        header: 'Name',
        dataIndex: 'Name',
        listeners: {
            headerclick: function() {
                var store = this.up('grid').getStore();
                store.sort({
                        property: 'SortOrder',
                        direction: this.sortState
                    });
            }
        }
    }
 ]