The sea urchin sperm receptor for egg jelly is a modular protein with extensive homology to the human polycystic kidney disease protein, PKD1.

Abstract

Abstract. During fertilization, the sea urchin sperm acrosome reaction (AR), an ion channel-regulated event, is triggered by glycoproteins in egg jelly (E J). A 210-kD sperm membrane glycoprotein is the receptor for EJ (RE J). This conclusion is based on the following data: purified REJ binds species specifically to EJ dotted onto nitrocellulose, an mAb to REJ induces the sperm AR, antibody induction is blocked by purified RE J, and purified REJ absorbs the AR-inducing activity of EJ. Overlapping fragments of REJ cDNA were cloned (total length, 5,596 bp). The sequence was confirmed by microsequencing six peptides of mature REJ and by Western blotting with antibody to a synthetic peptide designed from the sequence. Complete deglycosylation of REJ followed by Western blotting yielded a size estimate in agreement with that of the mature amino acid sequence. REJ is modular in design; it contains one EGF module and two C-type lectin carbohydrate-recognition modules. Most importantly, it contains a novel module, herein named the REJ module (700 residues), which shares extensive homology with the human polycystic kidney disease protein (PKD1). Mutations in PKD1 cause autosomal dominant polycystic kidney disease, one of the most frequent genetic diseases of humans. The lesion in cellular physiology resuiting from mutations in the PKD1 protein remains unknown. The homology between REJ modules of the sea urchin REJ and human PKD1 suggests that PKD1 could be involved in ionic regulation. SEA urchin eggs possess an extracellular matrix termed egg jelly (E J) t. Glycoprotein ligands in EJ induce the sperm acrosome reaction (AR) (Keller and Vacquier, 1994a;Suzuki, 1995). The AR is required for fertilization; it consists of the exocytosis of the acrosome granule and the polymerization of acrosomal actin to form the bindin-coated acrosomal process used by the sperm to attach to and fuse with the egg (Vacquier et al., 1995). Underlying the E J-induced AR, increased sperm respiration,

Coordinate Expression of the Autosomal Dominant Polycystic Kidney Disease Proteins, Polycystin-2 And Polycystin-1, in Normal and Cystic Tissue

“…The function(s) that the ADPKD proteins may have in these diverse cell types can as yet only be guessed at, with structural predictions suggesting a role in signaling, triggered by cell-cell/matrix interactions 5 or a possible involvement in ion transport. 4,6,32 In general, our results in nonrenal fetal tissues are consistent with those previously described for polycystin-1 27 but extend them by showing coexpression of the polycystin molecules by a wide variety of different cell types. Nevertheless, some questions remain.…”

3D structure of eukaryotic flagella in a quiescent state revealed by cryo-electron tomography

“…The only structural descriptions of similar membrane-bound materials have come from other investigations of frozen-hydrated sea urchin sperm (11), suggesting that this structure can only be preserved by rapid freezing techniques. One of the major membrane proteins of the sea urchin sperm flagellum is the glycosylated receptor for egg jelly (REJ1) (28). Shedding of the extracellular domain from this protein might be a mechanism by which the flagellar membrane removes contaminants or achieves release from obstacles (29).…”

A polycystin-1 controls postcopulatory reproductive selection in mice

“…The sea urchin acrosome reaction is triggered as sperm contact the jelly coat surrounding the egg by fucose sulfate polymer, a polysaccharide component of egg jelly (17). suREJ1, a polycystin-1-related protein in sea urchin sperm, binds fucose sulfate polymer and is a candidate subunit of the receptor that initiates acrosome reactions (18,19). Additional polycystin-1 proteins are also present and may participate in the signal transduction mechanism that leads to exocytosis (19,20).…”