Targeted Ablation of Plasma Membrane Ca2+-ATPase (PMCA) 1 and 4 Indicates a Major Housekeeping Function for PMCA1 and a Critical Role in Hyperactivated Sperm Motility and Male Fertility for PMCA4

Abstract

The relative importance of plasma membrane Ca 2؉ -ATPase (PMCA) 1 and PMCA4 was assessed in mice carrying null mutations in their genes (Atp2b1 and Atp2b4). Loss of both copies of the gene encoding PMCA1 caused embryolethality, whereas heterozygous mutants had no overt disease phenotype. Despite widespread and abundant expression of PMCA4, PMCA4 null (Pmca4 ؊/؊ ) mutants exhibited no embryolethality and appeared outwardly normal. Loss of PMCA4 impaired phasic contractions and caused apoptosis in portal vein smooth muscle in vitro; however, this phenotype was dependent on the mouse strain being employed. Pmca4 ؊/؊ mice on a Black Swiss background did not exhibit the phenotype unless they also carried a null mutation in one copy of the Pmca1 gene. Pmca4 ؊/؊ male mice were infertile but had normal spermatogenesis and mating behavior. Pmca4؊/؊ sperm that had not undergone capacitation exhibited normal motility but could not achieve hyperactivated motility needed to traverse the female genital tract. Ultrastructure of the motility apparatus in Pmca4 ؊/؊ sperm tails was normal, but an increased incidence of mitochondrial condensation indicated Ca 2؉ overload. Immunoblotting and immuno-histochemistry showed that PMCA4 is the most abundant isoform in testis and sperm and that it is localized to the principle piece of the sperm tail, which is also the location of the major Ca 2؉ channel (CatSper) required for sperm motility. These results are consistent with an essential housekeeping or developmental function for PMCA1, but not PMCA4, and show that PMCA4 expression in the principle piece of the sperm tail is essential for hyperactivated motility and male fertility.

Plasma membrane calcium ATPases (PMCAs) as potential targets for the treatment of essential hypertension

“…PMCA4 mRNA has been detected in endothelial and VSMCs of porcine aorta (Szewczyk et al, 2007), in VSMCs from mouse carotid artery , and was shown as the most prominent PMCA mRNA transcript in mouse whole aorta (Okunade et al, 2004). PMCA4 protein expression has been reported in a mouse VSMC line and in isolated murine aortic VSMCs .…”

“…Studies to date suggest that PMCA4 may modulate bulk Ca 2+ homeostasis, nNOS signalling (Pande et al, 2006 and eNOS activity (Holton et al, 2010). It is noteworthy that recent studies investigating PMCA4 in the cell cycle have concluded that its role is related both to its activity and its scaffolding effects )-this has been demonstrated using two mouse models, one in which there is a complete lack of PMCA4 protein, whilst the other has a mutant, non-functioning PMCA4 (Okunade et al, 2004;Schuh et al, 2004). The availability of the PMCA4 knockout mouse affords the opportunity for investigation of the effects of PMCA4 ablation on BP and arterial contractility.…”

“…PMCA1 is ubiquitously expressed in humans; ablation of PMCA1 is embryonically lethal early in mouse development leading to the suggestion that the protein has a 'housekeeping' or developmental role (Okunade et al, 2004;Brini, 2009;Kenyon et al, 2010). PMCA4 is also present in most cell types, but its function may be more tissue specific than PMCA1 (Schuh et al, 2004).…”

“…Global ablation of Atp2b1 in mice is embryonically lethal early in development, between 3.5 and 8.5 days of pregnancy, suggesting an important role for PMCA1 in development (Okunade et al, 2004;Shaheen, 2012). PMCA1 has been proposed to have a role in BP regulation as mice bred to be globally heterozygous for Atp2b1, whilst indeed viable, exhibit elevated BP (Fujiwara et al, 2014).…”

“…Mammalian PMCAs belong to a multigene family of four different genes (ATP2B1-4 in humans) which encode respectively for PMCA proteins 1-4. The protein expression of PMCA2 and 3 is limited, principally to neuronal-type cells, however, PMCA1 and 4 are expressed throughout the body (Carafoli, 1991;Keeton et al, 1993;Street et al, 1998;Okunade et al, 2004).…”