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Harvey M Florman

Publications and source records attributed to Harvey M Florman.

8 recordsLinked to original sources
PubMed2006

Functional characterization of PKDREJ, a male germ cell-restricted polycystin.

Polycystin-1 regulates a number of cellular processes through the formation of complexes with the polycystin-2 ion channel or with other signal transduction proteins. Polycystin-1 is expressed in many tissues but other members of this gene family are distributed in a more restricted fashion. PKDREJ expression has been detected only in the mammalian testis, where it is restricted to the spermatogenic lineage and retained in mature sperm. However, the functional characteristics of this protein and its role in sperm biology are not well understood. In this study it is shown that PKDREJ can modulate G protein signaling and associates with several members of the polycystin-2 family. These interactions, as well as polycystin-2 association with TRPC channels, are consistent with a role of this protein in the regulation of the acrosome reaction and in other aspects of sperm physiology.

Alternative Splicing↗
PubMed2004

Enkurin is a novel calmodulin and TRPC channel binding protein in sperm.

The TRPC cation channel family has been implicated in receptor- or phospholipase C (PLC)-mediated Ca2+ entry into animal cells. These channels are present in mammalian sperm and are assigned a role in ZP3-evoked Ca2+ influx that drives acrosome reactions. However, the mechanisms controlling channel activity and coupling Ca2+ entry through these channels to cellular responses are not well understood. A yeast two-hybrid screen was carried out to identify TRPC-interacting proteins that would be candidate regulators or effectors. We identified a novel protein, enkurin, that is expressed at high levels in the testis and vomeronasal organ and at lower levels in selected other tissues. Enkurin interacts with several TRPC proteins (TRPC1, TRPC2, TRPC5, but not TRPC3) and colocalizes with these channels in sperm. Three protein-protein interaction domains were identified in enkurin: a C-terminal region is essential for channel interaction; an IQ motif binds the Ca2+ sensor, calmodulin, in a Ca2+-dependent manner; and a proline-rich N-terminal region contains predicted ligand sequences for SH3 domain proteins, including the SH3 domain of the p85 regulatory subunit of 1-phosphatidylinositol-3-kinase. We suggest that enkurin is an adaptor that functions to localize a Ca2+ sensitive signal transduction machinery in sperm to a Ca2+-permeable ion channel.

Adaptor Proteins, Signal Transducing↗
PubMed2004

Bovine sperm capacitation: assessment of phosphodiesterase activity and intracellular alkalinization on capacitation-associated protein tyrosine phosphorylation.

Mammalian sperm capacitation is the obligatory maturational process leading to the development of the fertilization-competent state. Heparin is known to be a unique species-specific inducer of bovine sperm capacitation in vitro and glucose a unique inhibitor of this induction. Heparin-induced capacitation of bovine sperm has been shown to correlate with protein kinase A (PKA)-dependent protein tyrosine phosphorylation driven by an increase in intracellular cAMP. This study examines the possible roles of cyclic nucleotide phosphodiesterase (PDE) activity and intracellular alkalinization on bovine sperm capacitation and the protein tyrosine phosphorylation associated with it. Measurement of whole cell PDE kinetics during capacitation reveals neither a substantial change with heparin nor one with glucose: PDE activity is effectively constitutive in maintaining intracellular cAMP levels during capacitation. In contrast to a transient increase in intracellular pH, a sustained increase in medium pH by switching from 5% CO(2)/95% air incubation to 1% CO(2)/99% air incubation over 4 hr in the absence of heparin resulted in an increase in protein tyrosine phosphorylation and in the extent of induced acrosome reaction comparable to that observed following heparin-induced capacitation in 5% CO(2). These results suggest that increased bicarbonate-dependent adenylyl cyclase activity, driven by alkalinization, increases intracellular cAMP and so increases PKA activity mediating protein tyrosine phosphorylation. Quantitative analysis of the lactic acid production rate by bovine sperm glycolysis accounts fully for intracellular acidification sufficient to offset heparin-induced alkalinization, thus inhibiting capacitation. The mechanism by which heparin uniquely induces intracellular alkalinization in bovine sperm leading to capacitation remains obscure, inviting future investigation.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed2002

The state of the union: the cell biology of fertilization.

Fertilization is the process by which sperm and egg unite. An expanded understanding of the mechanisms that underlie these events has provided insights into an important aspect of early development and also has proven to be a valuable model in which to study cellular function. In addition, many emerging strategies for contraception and for the treatment of infertility are based on the mechanism of gamete interaction. Here, we discuss the cell and molecular biology of mammalian fertilization, highlight selected recent breakthroughs and attempt to identify key unanswered questions.

Animals↗