Comparative Endocrinology o f Calcium Regulation — Sunday

Comparative Endocrinology o f Calcium Regulation—Sunday Comparative Endocrinology Sunday, June 24, 2007 CE01 Calcium storage in sarcoplasmic reticulum: The role of calcium pumps and binding proteins during elevated influx in calcifying crayfish M. Wheatly, Y. Gao, C. Gillen, Z. Jamal Wright State University, Dayton, OH Kenyon College, Gambier, OH, USA The sarcoplasmic reticulum (SR) is the primary intracellular calcium (Ca) store (ICS). Mineralization events typically require mass vectorial Ca flux across epithelial cells. The role of the ICS in sequestering Ca at these times can be explored through examining expression of associated proteins including the Sarco/Endoplasmic Reticulum Ca ATPase (SERCA) and the Sarcoplasmic Ca binding Protein (SCP). The comparative model employed in our laboratory is the molting cycle of the freshwater crayfish where whole animal Ca influx is heightened in postmolt to effect cuticular mineralization as opposed to intermolt when the organism exhibits Ca balance. Epithelial tissues (antennal gland, renal; hepatopancreas, digestive) were compared with non-epithelial tissues (abdominal and cardiac muscle). Techniques of analysis involved real time PCR, Northern blotting, Western analysis, in situ, and immunofluorescence. SERCA and SCP expression were both downregulated in postmolt compared with intermolt stage, suggesting that their cellular functions are linked. Other studies in our lab have shown that Ca importers (epithelial Ca channel, ECaC) and basolateral exporters (Plasma Membrane Ca ATPase, PMCA; NCX, Sodium/Calcium eXchanger) both exhibit upregulation during postmolt vectorial Ca influx compared with intermolt. Collectively this suggests that there is reciprocal regulation between Ca transporting mechanisms on external (plasma) membranes and internal (SR) membranes. Seemingly the need for Ca sequestration in SR decreases when Ca is moving rapidly through epithelial cells en route to the extracellular fluid and thence to mineralization sites. Supported by US National Science Foundation grant IBN 0445202.