Construction and analysis of a human testis/sperm-enriched interaction network: Unraveling the PPP1CC2 interactome

• Published in: Biochimica et biophysica acta. General subjects Vol. 1861; no. 2; pp. 375 - 385
• Main Authors: Silva, Joana Vieira, Yoon, Sooyeon, De Bock, Pieter-Jan, Goltsev, Alexander V., Gevaert, Kris, Mendes, José Fernando F., Fardilha, Margarida
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01-02-2017
• Subjects: A Kinase Anchor Proteins - metabolism; DNA-Binding Proteins - metabolism; Humans; Infertility - metabolism; Infertility - pathology; Janus Kinase 2 - metabolism; Lamin Type A - metabolism; Male; Nuclear Proteins - metabolism; Phosphoprotein phosphatase 1; Protein Interaction Maps - physiology; Protein-protein interaction network; Receptor-Interacting Protein Serine-Threonine Kinases - metabolism; RNA-Binding Proteins - metabolism; Sperm Motility - physiology; Spermatogenesis - physiology; Spermatozoa; Spermatozoa - metabolism; Testis; Testis - metabolism; Testis; Phosphoprotein phosphatase 1; Spermatozoa; Protein-protein interaction network
• ISSN: 0304-4165; 1872-8006
• DOI: 10.1016/j.bbagen.2016.11.041

Phosphoprotein phosphatase 1 catalytic subunit gamma 2 (PPP1CC2), a PPP1CC tissue-specific alternative splice restricted to testicular germ cells and spermatozoa, is essential for spermatogenesis and spermatozoa motility. The key to understand PPP1CC2 regulation lies on the characterization of its interacting partners.
We construct a testis/sperm-enriched protein interaction network and analyzed the topological properties and biological context of the network. Further the interaction of a potential target for pharmacological intervention was validated in human spermatozoa.
A total of 1778 proteins and 32,187 interactions between them were identified in the testis/sperm-enriched network. The network analysis revealed the members of functional modules that interact more tightly with each other. In the network, PPP1CC was located in the fourth maximum core part (k=41) and had 106 direct interactors. Sixteen PPP1CC interactors were involved in spermatogenesis-related categories. Also, PPP1CC had 50 direct interactors, highly interconnected and many of them part of the network maximum core (k=44), associated with motility-related annotations, including several previously uncharacterized interactors, such as, LMNA, JAK2 and RIPK3.
In this study we integrated tissue-specific protein expression and protein-protein interaction data in order to identify key PPP1CC2 complexes for male reproductive functions.
One of the most intriguing interactors was A-kinase anchor protein 4 (AKAP4), a testis-specific protein related to infertility phenotypes and involved in all major motility-related annotations.
We demonstrated for the first time the interaction between PPP1CC2 and AKAP4 in human spermatozoa and the potential of the complex as contraceptive target.
•A testis/sperm-enriched protein interaction network was constructed and characterized.•PPP1CC2-based sub-networks for spermatogenesis and sperm motility were described.•Uncharacterized PPP1CC2 interactors were associated with key functions for male fertility.•The interaction between PPP1CC2/AKAP4 was demonstrated for the first time.