A CALCIUM RESPONSIVE ELEMENT THAT REGULATES EXPRESSION OF 2 CALCIUM-BINDING PROTEINS IN PURKINJE-CELLS

Calbindin D28 encodes a calcium binding protein that is expressed in t he cerebellum exclusively in Purkinje cells. We have used biolistic tr ansfection of organotypic slices of P12 cerebellum to identify a 40-bp element from the calbindin promoter that is necessary and sufficient for Purkinje fell specific expression in this transient ipl situ assay , This element (PCE1) is also present in the calmodulin TI promoter, w hich regulates expression of a second Purkinje cell Ca2+ binding prote in, Expression of high levels of exogenous calbindin or calretinin dec reased transcription mediated by PCE1 in Purkinje cells 2.5- to 3-fold , whereas the presence of 1 mu M ionomycin in the extracellular medium increased expression, These results demonstrate that PCE1 is a compon ent of a cell-specific and Ca2+-sensitive transcriptional regulatory m echanism that may play a key role in setting the Ca2+ buffering capaci ty of Purkinje cells.