protected function _setCollectionOrder($column)
 {
     $collection = $this->getCollection();
     if ($collection) {
         $columnIndex = $column->getFilterIndex() ? $column->getFilterIndex() : $column->getIndex();
         if (strpos($columnIndex, 'am_attribute_') !== FALSE) {
             $attribute = str_replace('am_attribute_', '', $columnIndex);
             $collection->addAttributeToSort($attribute, $column->getDir());
         } else {
             parent::_setCollectionOrder($column);
         }
     }
     return $this;
 }