THE HUMAN 180-KDA RECEPTOR FOR SECRETORY PHOSPHOLIPASES A(2) - MOLECULAR-CLONING, IDENTIFICATION OF A SECRETED SOLUBLE FORM, EXPRESSION, AND LOCALIZATION

Secretory phospholipases A(2) (sPLA(2)) are structurally related enzymes found in mammals as well as in insect and snake venoms. They have been associated with several physiological, pathological, and toxic processes. Some of these effects are apparently linked to the existence of specific receptors for both venom and mammalian sPLA(2)s. We report here the molecular cloning and expression of one of these sPLA(2) receptors from human kidney. Two transcripts were detected. One encodes for a transmembrane form of the sPLA(2) receptor and the other one is an alternatively processed transcript, caused by polyadenylation occurring at a site within an intron in the C terminus part of the transcriptional unit. This transcript encodes for a shortened secreted soluble sPLA(2) receptor lacking the coding region for the transmembrane segment, Quantitative polymerase chain reaction experiments indicate a 1.6:1 ratio between the levels of transcripts encoding for the membrane bound and soluble forms of the receptor, respectively. Soluble and membrane bound human sPLA(2) receptors both bind sPLA(2) with high affinities. However, the binding properties of the human receptors are different from those obtained with the rabbit membrane-bound sPLA(2) receptor. The 180 kDa human sPLA(2) receptor gene has been mapped in the q23-q24 bands of chromosome 2.