IDENTIFICATION OF A RAT GLOMERULAR MESANGIAL CELL MITOGENIC 5-HT(2A) RECEPTOR

Previous studies have demonstrated the presence of mitogenic serotonin [i.e., 5-hydroxytryptamine (5-HT)] receptors on glomerular mesangial cells and have linked those receptors to a complicated array of intrac ellular and autocrine/paracrine signaling pathways [T. Knauss and H. E . Abboud. Am. J. Physiol. 251 (Renal Fluid Electrolyte Physiol. 20): F 844-F850, 1986; and N. Takuwa, M. Ganz, Y. Takuwa, R. B. Sterzel, and H. Rasmussen. Am. J. Physiol. 257 (Renal Fluid Electrolyte Physiol. 26 ): F431-F439, 1989]. Those studies suggested that the mesangial subtyp e of 5-HT receptor is a member of the 5-HT2 receptor family, which con sists of three known members, designated as subtypes A, B, and C. The purpose of the current study was to identify the subtype of 5-HT2 rece ptor present on mesangial cells. Northern blot showed detectable mRNA for a putative 5-HT2A receptor, but not for 5-HT1A or 5-HT2C receptors . Reverse transcription-polymerase chain reaction (RT-PCR) with degene rate oligonucleotides derived from the putative third and sixth transm embrane domains of cloned 5-HT2 receptors yielded a 580-nucleotide (nt ) fragment. RT-PCR with primers highly specific for the 5-HT2A recepto r and designed to amplify > 95% of its coding block yielded a product of 1,320 nt. Nested PCR reactions yielded products of the predicted si zes for the 5-HT2A receptor. Partial sequence information was obtained , and the sequence corresponded exactly (627/627 nt) to that published for the cloned rat brain 5-HT2A receptor. These studies identify the mesangial cell mitogenic 5-HT receptor as a 5-HT2A receptor subtype.