Urinary Lipocalin Protein in a Female Rodent with Correlation to Phases in the Estrous Cycle: An Experimental Study Accompanied by In Silico Analysis

Ganesan Saibaba,Govindaraju Archunan,Hiroaki Matsunami,Rengasamy Lakhsminarayanan Rengarajan,Subramanian Muthukumar,Alagersamy Alagesan,Durairaj Rajesh

doi:10.1371/journal.pone.0071357

Ganesan Saibaba, Govindaraju Archunan + Show 5 more

Open Access

https://doi.org/10.1371/journal.pone.0071357

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Journal: PLoS ONE	Publication Date: Aug 14, 2013
Citations: 18	License type: CC BY 4.0

Affiliation: Bharathidasan University, University of Hong Kong

Abstract

Male urinary lipocalin family proteins, practically odorant-binding proteins but also could be pheromones by themselves, in rodents act as a shuttle for chemosignal communication and facilitate delivery of the signals for access to congeners. However, presence of this protein in urine of female rodents has not yet been reported. Therefore, the present investigation was carried out to find if lipocalin family protein is present in the urine of female house rat and, if so, to find whether its expression differs between the phases in the estrous cycle. The rat urinary protein was separated in single dimensional gel electrophoresis. A 14.5 kDa lipocalin protein appeared in the urine prominently during the estrus and metestrus phases compared to proestrus and diestrus phases. The expression of this protein in the urine was very low in ovariectomized rats. MALDI-TOF/MS analysis affirmed the 14.5 kDa protein as a lipocalin family protein. Analysis adopting bio-informatics tools further proved the protein as a lipocalin family member. Thus, this study for the first time demonstrated the presence of a lipocalin family protein in the urine of a female rodent and it was highly expressed during estrus phase. This lipocalin protein in female rat urine may facilitate a chemosignal function independently of a pheromone or in association with a specific pheromone.

Highlights

Chemosignals are small volatile compounds associated in one or more ways in synchronization of aspects of reproductive physiology between males and females and mediation of social responses [1,2]
It has been demonstrated that major urinary proteins (MUPs)-pheromone binding in male mice urine provides for a gradual release of the volatile ligand to the environment [11] thereby enhancing the longevity of the volatile
In the urine of male rat a volatile was found in a form bound to a-2u globulin [12], and pheromone-a-2u globulin binding was traced to the preputial gland which is one of the major sources of volatiles [5]

Summary

Introduction

Chemosignals are small volatile compounds associated in one or more ways in synchronization of aspects of reproductive physiology between males and females and mediation of social responses [1,2]. A comparable functional protein, a-2u globulin, has been identified in the rat [5] Both MUPs and a-2u globulin belong to the structural homology superfamily called lipocalin [6,7]. It has been demonstrated that MUP-pheromone binding in male mice urine provides for a gradual release of the volatile ligand to the environment [11] thereby enhancing the longevity of the volatile. This finding provides strong circumstantial evidence that the lipocalin (MUP) is capable of releasing the volatiles at a slow pace, suggesting a lead to a biological application. The lipocalin proteins present in the male possess the ability to bind and release the volatiles and participate in several pheromonebased effects in the conspecifics

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