title: Differential expression of lysosome-associated protein transmembrane-4 beta (LAPTM4B) in granulosa cells of ovarian follicles and in other bovine tissues.
abstract: BACKGROUND
  LAPTM4B is a member of the lysosome-associated transmembrane protein superfamily that is differentially expressed in normal human tissues and upregulated in various types of carcinomas. These proteins are thought to be involved in the regulation of cell proliferation and survival. The objective of this study was to investigate the expression of bovine LAPTM4B during ovarian follicular development and in various bovine tissues.
  
  
  RESULTS
  Northern blot analysis revealed a 1.8 kb transcript, with highly variable steady state levels among tissues. RT-PCR analysis showed that LAPTM4B mRNA transcripts were low in granulosa cells of small antral follicles, increased in large dominant follicles, and decreased in ovulatory follicles following injection of human chorionic gonadotropin (hCG; P < 0.003). Ovulatory follicles collected at various times after hCG injection revealed a significant reduction of LAPTM4B mRNA starting at 18 h post-hCG (P < 0.029). Immunoblotting analysis using antibodies generated against bovine LAPTM4B recognized proteins of 26.3 and 31.5 kDa in granulosa cells of developing follicles and corpus luteum. Further analyses of affinity-purified His-tag LAPTM4B overexpressed in HEK cells showed that the 31.5 kDa protein represented the ubiquinated isoform of the 26.3 kDa native protein. The 26.3 kDa protein was differentially expressed showing highest amounts in dominant follicles and lowest amounts in ovulatory follicles 24 h post-hCG. Immunohistochemical analyses of LAPTM4B showed marked heterogeneity of labeling signal among tissues, with LAPTM4B mainly localized to perinuclear vesicles, in keeping with its putative lysosomal membrane localization.
  
  
  CONCLUSIONS
  This study reports for the first time that bovine LAPTM4B in granulosa cells is present in both unubiquinated and ubiquinated forms, and is differentially expressed in developing ovarian follicles, suggesting a possible role in terminal follicular growth.
authors.affiliation: Centre de recherche en reproduction animale, Département de biomédecine vétérinaire, Faculté de médecine vétérinaire, Université de Montréal, P.O. Box 5000, St-Hyacinthe, Québec, J2S 7C6, Canada. k.ndiaye@umontreal.ca.
authors.forename: Kalidou
authors.initials: K
authors.lastname: Ndiaye
authors.affiliation: Centre de recherche en reproduction animale, Département de biomédecine vétérinaire, Faculté de médecine vétérinaire, Université de Montréal, P.O. Box 5000, St-Hyacinthe, Québec, J2S 7C6, Canada. paul.d.carriere@umontreal.ca.
authors.forename: Paul D
authors.initials: PD
authors.lastname: Carrière
authors.affiliation: Centre de recherche en reproduction animale, Département de biomédecine vétérinaire, Faculté de médecine vétérinaire, Université de Montréal, P.O. Box 5000, St-Hyacinthe, Québec, J2S 7C6, Canada. jean.sirois@umontreal.ca.
authors.forename: Jean
authors.initials: J
authors.lastname: Sirois
authors.affiliation: Centre de recherche en reproduction animale, Département de biomédecine vétérinaire, Faculté de médecine vétérinaire, Université de Montréal, P.O. Box 5000, St-Hyacinthe, Québec, J2S 7C6, Canada. david.w.silversides@umontreal.ca.
authors.forename: David W
authors.initials: DW
authors.lastname: Silversides
authors.affiliation: Centre de recherche en reproduction animale, Département de biomédecine vétérinaire, Faculté de médecine vétérinaire, Université de Montréal, P.O. Box 5000, St-Hyacinthe, Québec, J2S 7C6, Canada. jacques.lussier@umontreal.ca.
authors.forename: Jacques G
authors.initials: JG
authors.lastname: Lussier
mesh_terms: D000818:Animals; D015152:Blotting, Northern; D002417:Cattle; D005260:Female; D006107:Granulosa Cells / Q000378:metabolism*; D007150:Immunohistochemistry; D008565:Membrane Proteins / Q000096:biosynthesis*; D015513:Oncogene Proteins / Q000096:biosynthesis*; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D059467:Transcriptome; D054875:Ubiquitination
chemical_list: D008565:Membrane Proteins; D015513:Oncogene Proteins; D012333:RNA, Messenger