SULFATE RESTRICTION INDUCES HYPOSECRETION OF THE ADHESION PROTEOGLYCAN AND CELL HYPOMOTILITY ASSOCIATED WITH INCREASED (SO4(2-))-S-35 UPTAKE AND EXPRESSION OF A BAND-3 LIKE PROTEIN IN THE MARINE SPONGE, MICROCIONA-PROLIFERA

Sulfate is an important component relating to normal proteoglycan secr etion and normal motility in the marine sponge, Microciona prolifera. The following alterations were observed in sponge cells when sulfate f ree artificial sea water was used as the suspension medium: 1) impairm ent of aggregation, 2) loss of cell movements, 3) a marked reduction i n the secretion of the adhesion proteoglycan (AP). Reversal of this ef fect occurred if sulfate depleted cells were again rotated in sulfate containing artificial sea water. Motility and reaggregation of sulfate deprived cells could be completely restored by purified AP, but only if cells were first pre-conditioned in normal sea water. Comparisons o f (SO42-)-S-35 uptake between normal and sulfate deprived cells which had been treated to reduce preformed secretions showed a marked increa se in (SO42-)-S-35 uptake and incorporation which could be greatly aug mented in the presence of Ca2+/Mg2+. Excessive retention of AP in sulf ate starved cells demonstrated by immunostaining suggested that AP sec retion and cellular motility may be controlled by a sulfate dependent secretogogue or that undersulfated AP itself had developed a secretory defect. SDS-PACE of Triton treated cellular extracts demonstrated a 1 16 kDa (SO42-)-S-35 sulfated band which co-migrated with AP, but only in extracts derived from sulfate starved cells. Western blots prepared from such extracts incubated in the presence of a monoclonal anti-ban d 3 antibody demonstrated labelling of a single 97 kDa band only in ma terial from sulfate deprived cells. The absence of this component in n ormal cell extracts indicated that this protein may be involved in fac ilitated sulfate transport. This study lends support to a heretofore u nrecognized role for sulfate in cell motility and secretion. (C) 1995 Wiley-Liss, Inc.