Fer kinase/FerT and adherens junction dynamics in the testis: An in vitro and in vivo study
Chen,Yong-Mei; Lee,Nikki P.Y.; Mruk,Dolores D.; Lee,William M.; Cheng,Chuen-yan
Biology of Reproduction 69(2): 656-672
Publication date: 2003
Fer kinase is a 94-kDa cytoplasmic cell-cell actin-based adherensjunction (AJ)-associated nonreceptor protein tyrosine kinase(PTK) found in multiple epithelia including the testis, whereasFerT kinase (51 kDa) is the truncated testis-specific form ofFer kinase, lacking the Fps/Fes/Fer/CIP4 (products of oncogenesidentified in avian and feline sarcoma, encoding tyrosine proteinkinases) and the three coiled-coil domains versus Fer kinase.Yet the role(s) of Fer kinase in AJ dynamics in the testis remainslargely unexplored. We have used an in vitro model of AJ assemblywith Sertoli-germ cell cocultures and an in vivo model of AJdisassembly in which adult rats were treated with 1-(2,4-dichlorobenzyl)-indazole-3-carbohydrazide(AF-2364) to study changes in the expression and/or localizationof Fer kinase during AJ restructuring. Fer kinase/FerT was expressedby Sertoli and germ cells when cultured in vitro. Using an antibodyprepared against a synthetic peptide, NH-SAPQNCPEEIFTIMMKCWDYK-COOH,corresponding to residues 779-799 of Fer kinase in therat, which failed to cross-react with FerT kinase, for immunohistochemistry,Fer kinase was detected in the seminiferous epithelium in virtuallyall stages of the epithelial cycle. At stages XIII-VI, Fer kinasewas associated largely with round and elongating spermatids.At stages VII-VIII, Fer kinase associated almost exclusivelywith round spermatids with very weak staining associated withelongated spermatids. This stage-specific localization of Ferkinase in the epithelium was confirmed by using staged tubulesfor semiquantitative reverse transcription-polymerase chainreaction. Studies by immunoprecipitation revealed that Fer kinaseassociated with N-cadherin, -catenin, p120, c-Src (a putativePTK and the product of the transforming, sarcoma-inducing geneof Rous sarcoma virus), Rab 8 (a GTPase), actin, vimentin, butnot E-cadherin, afadin, nectin-3, and integrin ß1,suggesting Fer kinase associates not only with the actin-basedcell-cell AJ structures, such as the N-cadherin/catenin complex(but not the 6ß1 integrin/laminin and the afadin/nectincomplex), but also with intermediate filament-based cell-celldesmosomes. An induction in Fer kinase expression was detectedduring Sertoli-germ cell AJ assembly in vitro but not duringAF-2364-induced AJ disruption in vivo. Yet this AF-2364-inducedFer kinase plummeting associated with an induction in N-cadherin,ß-catenin, and p120, particularly at the base ofthe seminiferous epithelium. In summary, Fer kinase structurallyassociates with the N-cadherin/catenin protein complex in thetestis and can possibly be used to mediate signaling functionvia the cadherin/catenin protein complex.